It would be "impossible" for Labour to do a deal with the Liberal Democrats after the next election if Nick Clegg remained leader, a shadow minister has said.
The 2015 election could produce another hung parliament, forcing either David Cameron or Ed Miliband to seek support from one of the smaller parties to get into Downing Street.
In an interview with The Huffington Post, Lisa Nandy, shadow civil society minister and close ally of Miliband, said Clegg was "wedded" to "free market liberalism".
"The problem with Clegg is that he is from that economic liberal wing of the party. It's very very difficult to see what Labour has in common with someone like Nick Clegg. There are other people in the Liberal party who might perhaps be different," she said.
"So if they had a different leader and stood on a social progressive manifesto I think that would be a different story. But if they stand on the sort of record that they have got in this government, I think it would be impossible. Because, quite simply, we don’t have enough philosophically in common to be able to form a lasting coalition."
Clegg has frequently insisted that single-party government would threaten Britain's economy. He told the CBI last week that the Lib Dems would "fight tooth and nail to get back into government again".
The deputy prime minister has not said he will quit after the election. However leadership candidates are already positioning themselves should he choose to step down. Tim Farron and Vince Cable, who are both on the left of the party, are both likely leadership candidates that Nandy and others on the Labour frontbench would find acceptable.
However the Lib Dems, who have remained loyal to Clegg despite the trauma of coalition with the Tories, would be unlikely to take kindly to Labour demands that they ditch their leader.
The surge of support for the SNP in Scotland has also seriously damaged Labour's chances of being able to secure an overall majority in 2015.
The Scottish nationalists' new leader, Nicola Sturgeon, has indicated she would be willing to prop up a Labour government in Westminster. However her demand that Miliband abandon the renewal of the UK's nuclear weapons arsenal would be a significant barrier.
In the full interview, Lisa Nandy speaks to Mehdi Hasan about Ed Miliband, Ukip and being asked out on dates by voters.Suggest a correction