PM position on Europe 'incoherent'
Labour is to ramp up its attack on David Cameron over his pledge of an EU referendum, warning that a British exit would please Vladimir Putin.
Shadow Europe minister Pat McFadden will brand the Prime Minister's position "incoherent" and insists the threat from Russia demands "common action and resolve" in Europe.
The intervention, in a speech to the Fabian Society, will be seen as a bid to open a new flank in the battle over EU policy.
Labour leader Ed Miliband has previously stressed the uncertainty for business and the economy an in-out referendum would generate. The party would only hold such a vote if there was a further transfer of powers to Brussels.
But Mr McFadden will argue that "security" is an increasingly important reason for staying in the union.
"This is about values," he will say. "Being part of the EU requires a commitment to peace, democracy, the rule of law, human rights and respect for borders.
"The European Union has stood together to agree sanctions against Russia in response to its proxy war in Ukraine. The security dimension of our membership of the EU is becoming much more important than before.
"The hard edge of our security will continue to be provided by Nato, but the commitment to the common values represented by the EU is crucial.
"While Eurosceptics crave the breaking of ties to the EU the security situation demands common action and resolve. "
Mr McFadden is to claim that Moscow has tried to help "anti-EU forces of the populist left and right".
He will also lash out at Ukip leader Nigel Farage for describing the Russian president as "an operator".
"If the EU were to splinter or split, no one would be more pleased than President Putin," the Labour frontbencher is to say.
"It is not an accident that the political forces President Putin admires are those anti-EU forces of the populist left and right."
Mr McFadden will argue that Mr Putin's aggression "is not confined to Ukraine", highlighting fears of EU members that share a border with Russia and incidents where the RAF have had to escort bombers from UK airspace.
"It is clear what is happening. We are being tested," he will say.
"Whenever the West has been tested in the past, it has looked to Britain. Today, such is the confusion and incoherence of the British government's position, some are no longer looking.
"As military chiefs have pointed out, on Ukraine and other towering issues of global security this government has been content to preside over a shrinking of Britain's role, leaving us a more marginal player on the international stage.
"Britain's debate about its future relationship with the EU risks almost entirely ignored the issue of our collective security.
"This is a mistake we can no longer afford. It is utterly incoherent for our Prime Minister to call for tougher European action against President Putin in one breath and then threaten to leave the EU in the next.
"Security is the unspoken dimension of this European debate. This is no time for democratic nations to consider breaking from their allies."
Mr McFadden will add: "This is a time when Britain and Europe should to stick together in the face of the threat we face.
"Instead, we have a Prime Minister whose approach to Europe has become characterised by posture, pandering and panic in the face of its own backbenchers and Ukip."