David Cameron will take his political tightrope act over Britain’s EU membership back on the road today with another intensive round of diplomacy.
Following a Prime Minister’s Questions session where the issue will inevitably feature, Mr Cameron will head to Brussels for a summit where he is to hold talks with key players.
The latest stage of his renegotiation drive comes after the European Referendum Bill romped over its first Commons hurdle, receiving its second reading from MPs with a majority of 491.
An SNP wrecking amendment calling for 16 and 17-year-olds to be allowed to take part - and requiring majorities in each of the four UK nations before "Brexit" occurs - was also seen off by margin of 279.
But Mr Cameron is still struggling to maintain Tory discipline amid growing demands for ministers to be given the freedom to campaign for Brexit.
London mayor Boris Johnson, a member of the premier’s political cabinet, has become the latest to call for collective responsibility to be suspended when the poll comes.
"I don't see why not myself," he said. "I think, probably, it would be safer and more harmonious just to say, 'Okay, you make your minds up'. I think, on something like this, do you really need to bind everybody in?"
He insisted that if Mr Cameron got the deal he wanted in Europe, "the overwhelming majority of his colleagues - on both the front and the back benches - will support him".
Mr Cameron appeared to warn ministers that they would be sacked for campaigning against the Government line over the weekend. But after a welter of criticism from senior Tories he insisted he had been “misinterpreted” by journalists and it was too early to take a decision on how the situation would be handled.
Asked about Mr Johnson's comments, the Prime Minister’s spokeswoman said: "He is clear that he thinks the approach during the referendum is an issue for further down the road, we need to take this step by step, the focus very much now is on renegotiating our relationship and addressing the concerns of the British people."
Eurosceptics, including former cabinet minister Owen Paterson, have claimed the Government could try to "fix" the referendum by scrapping the usual purdah restrictions preventing the publication of promotional material by Whitehall before a poll.
Number 10 defended the position, saying Mr Cameron had been clear that "the Government is not going to be neutral on this".
Challenged about the move in the Commons, Foreign Secretary Philip Hammond said there were "operational and political" reasons for lifting the restrictions but insisted that the Government did not plan to "spend large sums of public money" campaigning.
If the restrictions were not lifted they "would stop the Government from 'publishing' material which deals with 'any issue raised by' the referendum question", Mr Hammond told MPs.
Meanwhile, former foreign secretary David Miliband ratcheted up the pressure on Mr Cameron by delivering a stark warning that Britain would be effectively “resigning from the world” if it left the EU.
In words that will fuel speculation he intends to take a prominent role in the campaign, Mr Miliband told CNN no US president would take the country seriously if it was not in the union.
The ex-MP - who moved to New York to run the International Rescue Committee charity after losing out to brother Ed in the 2010 Labour leadership contest - said: “Even the talk of Britain leaving the EU is damaging for Britain and the reality would be disastrous.”
Mr Miliband said he had not been following the debate over whether Labour figures should share a platform with David Cameron if he is campaigning to stay in the union - a prospect ruled out by the three main contenders yesterday.
But he added: “The absolutely vital point is that the economic, the political, the international reasons for Britain to remain a key part of the EU are put front and centre.
“It is completely evident to me that no American government would ever take seriously a Britain that has withdrawn from the EU. It would be almost like Britain was resigning from the world.”
After PMQs, Mr Cameron will attend the EU-CELAC meeting of European, Latin American and Caribbean nations in Brussels.
He is expected to have talks with Cypriot president Nicos Anastasiades, followed on Thursday by meetings with Belgian prime minister Charles Michel, Spanish counterpart Mariano Rajoy, Finland's Juha Sipila and Romanian president Klaus Iohannis.
The Prime Minister's spokeswoman said: "This is part of the PM's ongoing approach to talk each leader through why he thinks this is the right approach and the concerns of the British people that he wants to seek to address during the renegotiation.
"His intention is to speak to all of them before the June European council."