David Cameron will urge business leaders on Thursday to speak out and help him keep Britain in the EU, as he attempts to launch his referendum campaign with a barrage of corporate support.
Mr Cameron, speaking at the World Economic Forum in Davos, will urge business leaders to overcome their fears of entering the political domain, declaring: "This is a once-in-a-generation moment and the stakes are high."
The prime minister is acutely aware that business leaders only belatedly entered the Scottish referendum debate in 2014, but argues that their voice was influential when it was finally heard.
Mr Cameron's aides and pro-EU campaigners have been holding private talks with business chiefs to urge them to speak out early in the referendum campaign, which is expected to start next month.
"The voice of business must be heard in Britain and across the whole continent," Mr Cameron will tell an audience of global business and financial chiefs at the Swiss resort.
"If you want a more competitive Europe, where the single market is completed, where there are more trade deals and fewer regulations: join me in making that case.
"If you believe, like I do, that Britain is better off in a reformed European Union, then, when the time comes, help me make that case for Britain to stay."
Some business chiefs will recall that Sajid Javid, the Eurosceptic business secretary, reprimanded them last year for speaking out in favour of Britain's EU membership before Mr Cameron concluded his negotiations.
But Mr Cameron is confident other European leaders will cut him a deal at a summit in Brussels on February 18-19, allowing him to sell a package of reforms to the British people in a referendum.
The prime minister is already thinking beyond a deal in Brussels and is considering how to launch the referendum campaign that will begin almost as soon as he returns to London.
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Mr Cameron will put his package of reforms — covering areas such as competitiveness, sovereignty and migration — to the cabinet for approval: he wants the deal to form the basis of his campaign to keep Britain in the EU.
Ministers expect Mr Cameron to convene the cabinet over the weekend of February 20-21 or on the following Monday at the latest. Some ministers will reject the deal and campaign for a Brexit.
Pro-European campaigners expect the Brussels deal to pave the way for a June referendum and have pencilled in June 23 as the most likely date. A September poll is the other option.
But under either scenario, the Britain Stronger in Europe campaign, the main "Remain" group, has been urging business leaders to launch an opening salvo in support of Mr Cameron.
"We've been told to keep our powder dry until after Cameron does the deal but then to speak out early and loud," said one business figure briefed on the plan.
The reluctance of some business leaders to speak out so far reflects their fear that if they express a view — on either side of the debate — they might upset many of their customers and their employees.
Donations to either campaign would require shareholder approval and many chief executives are expected to conclude they have little to gain from entering the debate.
Corporate Britain took a similar view in the Scottish referendum until the last few weeks, when opinion polls suggested there was a serious risk of the UK splitting up.
Polls on the Brexit referendum put both sides roughly neck-and-neck, although some surveys in recent days have put the Leave campaign ahead, highlighting the uncertainty of the final result.
Carolyn Fairbairn, the new head of the CBI employers' federation, has said "most of our members want to be in a reformed EU because of the benefits of the single market" but she would listen to those members who wanted to leave.