Labour has been accused of being too tribal in its attitude towards the Lib Dems, and warned it stands no chance of forming a coalition with the third party in the event of another hung parliament.
Speaking at a Centre Forum conference fringe event in Liverpool, Lib Dem MP for Manchester Withington, John Leech, said while the two parties had a lot of common ground on constitutional reform, Labour didn't have the right attitude for a party with which to share power.
"The problem that we have is Labour don't seem to understand what coalition politics is all about," he said.
"Having effectively left us with no option but to have a coalition with the Tories, Labour's response has been to complain about everything. They like being in opposition.
"Until Labour grows up and takes a pragmatic position on a potential coalition in the future, there is little chance of us being in coalition together. If we are going to work together in the future, there is going to have to be some give and take on both sides.
"Labour need to accept that coalition politics are here to stay."
Shadow health minister and Labour MP for Islington Emily Thornberry refused to countenance the idea of a Lib/Lab coalition, arguing the next election would render it a moot point.
"Far too many people were misled for far too long about what the Liberal Democrats were. The liberals will not survive the next general election," she argued, somewhat contemptuously.
"People will not forgive them propping up this Tory government. If it wasn't for the Liberal Democrats this government would not be able to continue. There will be polarised politics at the next election and that will be to Labour's advantage."
But backbench Labour MP Ben Bradshaw was more optimistic, saying: "If you look at both our histories, you do see a common strand which is very distinctive from the Conservative one. We certainly have more in common with each other than with the Conservatives.
"Look at the electoral map. The vast majority of seats that we [Labour] need to win are against Tories. That's going to be even more the case if the boundary changes go through. It's manifestly in the centre left's interests to form a commonality in policy and approach."
He added: "A collapse in the Liberal Democrat vote doesn't help Labour nearly as much as it does the Tories."
Bradshaw said that Emily Thornberry's hostility was based on her local experiences in north London, where, according to Bradshaw, she had to fight "the most hideous Lib Dems".
Thornberry nodded in agreement, adding: "I think it was a bloody cheek of the Lib Dems to tell us to get rid of Gordon Brown"