Jeremy Corbyn's deputy has admitted he is "worried" about the level of sniping by MPs at the new leader and appealed for them to give him time to "lay out his stall".
Tom Watson flatly dismissed the prospect of "serious" politicians defecting to the Liberal Democrats - joking that it would be like "leaving the Beatles to join a Bananarama tribute band".
But he voiced concerns that some MPs did not appear to accept the veteran left-winger's overwhelming victory in the leadership contest.
The comments, in an interview on BBC Radio 4's Today programme, came amid warnings that Mr Corbyn has "months rather than years" to present Labour as a credible alternative to the Tories.
Backbencher Stephen Kinnock told BBC Radio 4's World at One: "What we need very soon is cohesion. Cohesion is crucial for credibility. That has to happen."
Shadow justice secretary Lord Falconer, a close friend of Tony Blair who served in the former prime minister's government, set out differences with the new leader on a wide range of policy areas, including defence, foreign affairs, welfare, education and the economy.
Meanwhile, shadow foreign secretary Hilary Benn rejected Mr Corbyn's opposition to the renewal of Trident, arguing that Britain needs to "maintain an independent nuclear deterrent."
But Mr Watson said there was "bound to be a bit of turbulence" as Mr Corbyn spelt out how he would manage the party.
"I would just say to those MPs that are saying things on the record and off the record, please respect the mandate he has been given," he said.
"Give him a bit of space and time to lay out his stall. We have got a party conference next week, we have got a shadow cabinet and an NEC meeting this Thursday.
"It will take time but you will see a change of direction and you will be able to see what Jeremy Corbyn really stands for."
Asked about the possibility of defections, Mr Watson said: "That would be like leaving the Beatles to join a Bananarama tribute band. I don't see any Labour MPs - serious Labour MPs - who are going to defect to go to Tim Farron's party."
However, he conceded that the level of sniping among MPs was a problem.
"I am worried about it, because I am not sure if some of our colleagues in the parliamentary party are prepared to accept the mandate he has been given," he said.
"I just ask them to show a little bit of respect and tolerance for him as a new leader assembling his team, he needs a bit of space and time to do that.
"Our MPs have to understand they are part of a democratic party now that is going to change and we have to respect the mandate he has been given."
Lib Dem leader Mr Farron said Labour had decided it was not "incredible" enough at the election and was heading deeper into "fantasy land".
Asked about Mr Watson's jibe, he told Today: "It's quite a good gag, but he's flattering himself if he thinks he would ever have been in the Beatles ...
"Nothing wrong with Bananarama."