Around 750,000 British teachers, civil servants, border agents and other public sector workers went on strike on Thursday after negotiations with the government failed to come to a resolution over proposed pension reforms.
Other campaign groups - including the protest movement UK Uncut and student groups - have said that they will coordinate demonstrations in support for the strike against the government's austerity reforms, which include 80 billion pounds ($130 billion) in public spending cuts.
Union leaders and campaign groups have warned that Thursday's action is the first of several over the summer, as public sector workers face up to a future of salary freezes and shrinking pensions.
Public sector strikes are rare in the UK, and labor unions had declined as political voices since the 12-month strike by miners in 1984 and 1985, which became a defining image of the Thatcher government.
In a meeting at Westminster cathedral hall on the eve of the strike, Public and Commercial Services Union (PCS) general secretary Mark Serwotka told members: "This is the most important strike in the history of our union. Everything we have ever worked for is under attack. Thousands of jobs are at stake, lower pensions are set to cost three times as much, and pay is frozen while inflation soars."
The Trade Union Congress' general secretary, Brendan Barber, is due to tell a rally in Exeter, in the UK's south west, that the pension reforms, combined with changes to tax regulations and pay freezes, represent "a gold standard for unfairness."
He is expected to say that the burden of reducing the country's deficit is being shifted away from the financial sector, which many see as having caused the economic crisis, and onto low-paid public sector workers.
This has become a catchphrase among opposition groups, who have said repeatedly that cuts need to be moderated in favor of policies that promote growth. The unions, including the PCS, have been vocal in their broad-based opposition to government spending cuts, despite their traditional role of fighting battles on narrower issues.
The Conservative Party, the senior member of the UK's coalition government, has tried to cast the strike as an attack on the "average, hardworking" British man or woman on the street.
Cabinet Office minister Francis Maude told the BBC Thursday that, "It is absolutely unjustifiable for parents up and down the country to be inconvenienced like this, forced to lose a day's work when they are trying to go out to work to earn money to pay the taxes that are going to support teachers' pensions."
"I think the challenge for the union movement is to articulate what they think the alternative is," Will Straw, associate director at the Institute for Public Policy Research, told CNBC.com.
Some of the unions have associated themselves with a movement called the Coalition of Resistance, which formed in the autumn of 2010 in solidarity with Greek protestors. That group has proposed a number of measures prioritizing growth over austerity.
"I looked at their plans when they were released at the end of last year and did an analysis of their deficit-reduction strategy. It didn't stack up. The numbers weren't there," Straw said.
"They're right to recognise the risks of the George Osborne austerity approach - that you could end up hampering growth to the extent that you end up jeopardising deficit goals. But they're not sufficiently cautious about a credit rating agency downgrade and what that would do to the cost of repaying government debt," he explained.
As groups like the Coalition of Resistance, which has been building its relationships with other protest and campaign groups ahead of tomorrow's strike, demonstrate, the union movement and its allies have become far better at mobilizing support than ever before.
Earlier in the year anti-austerity protests and demonstrations against university tuition fees saw the unions front-and-centre as political voices.
"There's been a lot of learning by the union movements in the UK from some of the more effective parts of political campaigning and political messaging in the US," Straw said. "I think it's fair to say that some of the trade unions in the UK, and particularly the TUC, are in the forefront of campaigning techniques in thinking about using new media, in linking to other progressive organizations, campaigning groups and NGOs. It will be very interesting to see if in this battle they can use it to full effect."
As well as the rise of new media channels – organizing through social networks is now a standard part of the protest movements – there is the simple fact that many people feel disenfranchised and unable to find a strong voice opposing cuts.
The main opposition, the Labour Party, were incumbent when the financial crisis struck, a fact which dented their credibility when discussing economic issues according to several party insiders. The party, whose leader Ed Miliband has publicly opposed Thursday's strike action, has a more moderate fiscal adjustment agenda.
Miliband wrote on his blog that the strike represented "a failure on both sides".
As Andrew Burgin, secretary of the Coalition of Resistance, told CNBC.com, many in the unions and the broader anti-cuts movement feel betrayed by Miliband's rejection of their cause.
The unions remain a major financial backer of the Labour Party, and there is considerable discontent at the lack of pro-union, pro-strike voices in the shadow cabinet, Burgin said.
However counterintuitive it may seem, union movements may in fact be profiting from a political vacuum created by an inability among the traditional center-left across Europe to articulate a coherent argument against cuts.
A socialist government in Greece has just passed a deep austerity package, another socialist government in Portugal has just been replaced, and Spain's socialists are under pressure over similar concerns.
In Southern Europe, as in the UK, new groups are forming and older union structures and allegiances are evolving or being abandoned, analysts said.
"I will say that the mass action in Greece in part reflects how austerity has caused a breakdown of the traditional industrial relations arrangements. Older unions have been hollowed out, and newer, inchoate structures among the unemployed and those in the informal sector are in the process of formation," Professor Craig Phelan, an expert in labor unions at the University of Kingston wrote in an email to CNBC.com.
Phelan also noted that while union membership has been declining for some time in Europe, these movements can rise rapidly.
"Trade unions do not grow incrementally," he said. "They grow in mighty leaps, in great upsurges. No one can guess when these upsurges will take place, but it is possible that we are experiencing the beginnings of one now."
As Glenis Willmott MEP, leader of the European Labour Party, acknowledged to CNBC.com, "We're struggling to find our voice across Europe because … socialist governments have been blamed for the economic crisis. The fact that it's been a global crisis hasn't seemed to resonate with the public. The existing governments are the ones that have been blamed.
"They have been accused of overspending, high public debt, bloated government, and the idea that government has become too big, and it bears responsibility for public debt, has stuck, and we've been punished for that," she said.
Likewise, socialist governments have been associated with greater freedom of labor across the EU, which, in periods of slow job growth and high unemployment, is socially and politically unpopular, Willmott added.
Some observers have noted that some anti-austerity movements are, as with the Arab Spring protests, not so much political as anti-political, representing a rejection of the status quo without backing any individual alternative.
Giovanni Grevi, a senior researcher at the Spanish thinktank FRIDE, told CNBC, "There is a crisis of the party political system, not least due to the fact that there are new means of political mobilization and participation through new technologies, and therefore a new ability of individuals and networks to set their own agenda and challenge the sort of top-down guidance from political parties and other established bodies in party politics and politics at large.
"There is a sort of bottom-up pressure that is enabled by the technology that seems to be very much finding fertile ground between young people whose allegiance to traditional ideologies has been waning for some time," Grevi said.
"In the face of the crisis there are different means and different alignments shaping up from the bottom to take part in political life and to put pressure on political parties."
This is the genesis of J30, a coordinating group emerged from a disparate group of activists, union members, students and "what you might call anarchists" from outside the traditional political spectrum, and is assisting in the planning of Thursday's strikes and protests, according to Glyn Harris, an organizer with the group.
Harris said that this incoherence and diversity is a reflection of the fact that the mainstream political voices are failing to pick up on their message.
To the criticism that the lack of a coherent anti-cuts argument would undermine the UK's ability to raise money in the capital markets, Harris said that the protestors, by and large, feel that the market's role in governing their country is unduly large. He explained that he and other protestors were concerned that the market's fears were being exploited to give the UK "a Chile moment" whereby neo-liberalism would be imposed through market mechanisms.
However, speaking not long after the Greek parliament rejected the voices of protesters in Syntagma Square and passed austerity packages, Harris, a veteran activist and campaigner, acknowledged that progressive movements had been through enough false dawns to make him realistic about the prospect of Thursday's action.