Labour leader Ed Miliband today appealed to disenchanted Liberal Democrats to work with him against the coalition Government.
He called on Lib Dems concerned that their party's alliance with the Tories was shifting Britain "to the Right" to submit ideas to Labour's policy review.
Shadow minister Liam Byrne would be working with former Lib Dem policy director Richard Grayson on the project, Mr Miliband said.
He identified the economy, electoral reform and issues surrounding social mobility as areas in which many Lib Dems shared similar interests to those of Labour or even the same interests.
"To those who are reluctant to abandon ship but are concerned about the direction of their party, I invite them to work with us on issues of common interest," he said at a Westminster press conference.
Labour's policy review would be asking for ideas from outside the party who "share our values, specifically from the Liberal Democrats".
"I have asked Liam Byrne to work with Richard Grayson to draw up areas where our policy review can be informed by submissions and ideas of Liberal Democrats who want to contribute," he said.
"To Liberal Democrats who fear their deal with the Tories is shifting the gravity of British politics to the Right, I invite them to work with us against the direction in which this Government is taking Britain.
"I look forward to hearing what they have to say and working with them."
Mr Miliband said he wanted to work with Lib Dems to try to "define the battleground" of British politics.
"The kaleidoscope of British politics has been shaken up and I don't think the pieces have properly settled," he said.
The Labour leader claimed thousands of Lib Dems had already joined his party but that the initiative was not simply about attracting defectors.
"I obviously welcome people who want to come over to the party, that's clearly the case, but that's not the only or even the primary purpose of this," he said.
"I think they were right on some issues around civil liberties during the last parliament, and I've acknowledged that.
"I think there is a commitment around parts of the Liberal tradition around green politics, for example, and the importance of climate change and the future of our country.
"I think also there is a commitment among many people to fairness."
But he added that there was a "wider point" about "who defines the battleground of British politics?"
"What David Cameron and (Deputy Prime Minister) Nick Clegg want to do together is define the battleground of British politics in a particular way," he said.
"And I think it strengthens our hand to work with others who want to define it a different way."
Mr Miliband said there were three principal areas which "defined the difference" between him and Prime Minister David Cameron and where Labour could work with the Lib Dems:
:: Social mobility, damaged by school budget cuts, university tuition fee increases, and the abolition of the education maintenance allowance;
:: The economy, on which the Government was taking a "far riskier" path than that set out by Labour;
:: Politics, with both Mr Cameron and Mr Clegg breaking pre-election promises.
Asked whether he would share a platform with Mr Clegg in campaigning for the Alternative Vote (AV) ahead of the referendum planned for next May, Mr Miliband said he would not rule it out.
"I think we can fight elections, as I am determined to do, against Liberal Democrats and the Conservatives, but also say there is an issue about changing our politics," he said.
However, he also stressed that those wanting to introduce AV must avoid it becoming a referendum on Mr Clegg.
"There is a danger of that, and if it becomes a referendum on Nick Clegg, I think given the way things are, we are going to have trouble winning it," he said.