* UK wants no border posts between Ireland and N.Ireland
* Government attempts to minimise post-Brexit disruption
* Dublin calls ideas timely and helpful
* Opposition Irish lawmaker attacks 'smugglers' charter' (Updates after publication of paper)
LONDON/DUBLIN, Aug 16 (Reuters) - Britain has said there should be no border posts or immigration checks between Ireland and the British province of Northern Ireland after Brexit, in a paper that attempts to resolve one of the most complex aspects of its departure from the European Union.
Some 30,000 people cross the 500-km (300-mile) border every day without customs or immigration controls; negotiators must work out new arrangements without inflaming tensions in a region that suffered decades of bloody turmoil before a peace deal in 1998.
As part of a series of papers that Prime Minister Theresa May hopes will push forward talks with the EU, the government on Tuesday outlined its vision for a "frictionless" customs system, which drew criticism from some in Brussels.
Wednesday's publication drew heavily on those proposals as a solution for Northern Ireland that would not involve "physical border infrastructure and border posts".
"The paper provides flexible and imaginative ideas and demonstrates our desire to find a practical solution that recognises the unique economic, social and cultural context of the land border with Ireland, without creating any new obstacles to trade within the UK," Northern Ireland minister James Brokenshire said in a statement.
The government said reaching an agreement with the EU that there should be no border infrastructure was top of Britain's list of priorities.
May also said Britain would consider stepping in to replace some EU funding for peace projects in Northern Ireland after it leaves the bloc in March 2019, to prevent a resurgence of violence between pro-British Protestants and Catholic Irish nationalists.
Commenting on an advance briefing of the position paper, the Irish government said it was "timely and helpful" and that it hoped enough progress could be made to move talks forward.
"Protecting the peace process is crucial and it must not become a bargaining chip in the negotiations," it said.
But Senator Mark Daly, deputy leader of Ireland's opposition Fianna Fáil party, said the proposals for a frictionless border appeared "more like fiction, and clueless on this island".
"It will be a smugglers' charter," he told BBC Radio Four.
Northern Ireland sold 2.7 billion pounds ($3.5 billion) of goods into Ireland in 2015, according to official figures, and many businesses have complex supply chains that involve crossing the border multiple times during the production process.
NO IMMIGRATION CHECKS
Britain said it wanted to maintain the Common Travel Area (CTA), a pact that allows free movement between the United Kingdom and Ireland for British and Irish citizens, with no need for passport controls and "no question of new immigration checks operating between Northern Ireland and Ireland".
That would mean EU citizens wishing to enter Britain could do so by travelling legitimately to Ireland and crossing the border unchecked - something that is likely to antagonise the many Britons for whom controlling immigration was a key reason for backing Brexit.
The government said control over migration from the EU into Britain could be exercised by restrictions on access to the British social security system and labour market. Further details would be set out in a future document on immigration.
Britain also wants to introduce new 'trusted trader' arrangements to help larger companies and make smaller firms exempt from customs processes.
It rejected the idea of an effective customs border in the Irish Sea that separates England, Wales and Scotland from Ireland and Northern Ireland as "not constitutionally or economically viable".
The border is one of three priority issues that the EU is insisting must be dealt with during the opening rounds of talks before moving on to Britain's future relationship with the bloc.
But Britain said it did not make sense to seek final agreement on Northern Ireland by October before moving ahead to the future relationship, because the two issues were inextricably linked.
The first two rounds of divorce talks in Brussels have made limited progress and Britain is keen to push them forward by publishing documents outlining its vision for future ties.
Tuesday's proposals on customs arrangements ideas met with scepticism among some of Britain's current EU partners, with one EU official describing the idea of an invisible border as 'fantasy'. ($1 = 0.7772 pounds) (Additional reporting by Estelle Shirbon in London; Writing by William James and Elizabeth Piper; Editing by Kevin Liffey and Mark Trevelyan)