Criticism of Jeremy Corbyn from right-wing Labour MPs should be "less feral, less hysterical and more constructive", the leader of the Unite union has said.
Len McCluskey said there was "nothing wrong with criticising the leadership", but urged the critics to be a "little bit more constructive" about supporting the Labour leader.
And Mr McCluskey told ITV's Peston on Sunday that if there was a rule in the party "against stupidity", then former London mayor Ken Livingstone and "lots of other people should have been excluded".
Mr McCluskey was quizzed on his views on Labour MPs who do not toe the line.
He said there was a "small rump" of right-wing Labour MPs who "continually criticise" Mr Corbyn: "Day in day out, the first thing they thought about was how do we criticise and attack."
Asked whether they should be deselected by their local parties, Mr McCluskey replied: "Accountability has always been there within the Labour Party, there's always been trigger balance for MPs.
"My view is that these particular MPs - there's nothing wrong with criticising the leadership if you have a particular view - but it should be less feral, less hysterical and more constructive.
"And that way we will have a better chance of having a united party in order to gain power, and that's what we want: we want a Labour government to give us a better Britain."
On anti-Semitism, Mr McCluskey was asked whether Mr Livingstone, who is suspended from the Labour Party due to his claim that Hitler supported Zionism in the 1930s, should be kicked out.
He replied: "If there was a rule in the party against stupidity, then he and lots of other people should have been excluded, because it was bizarre, and I said it at the time, what he came out with.
"I'm not interested in the historical references, but the reality is there is a process so I'm not the judge and jury in that sense.
"The process has to come through, it needs to be done very quickly now and I think under the new leadership of the Labour Party we'll get to the bottom of this issue of anti-Semitism.
"But I reject the idea that my party - a party that I have been in for 47 years - is a toxic Labour Party that is anti-Semitic and misogynistic - that's just nonsense."
Mr McCluskey also denied that there is a "glass ceiling" in Unite, which has a median gender pay gap of 29.6%.
He said: "My union has got 72% male, and we draw our officers from our membership so there is a proportion of our officers within our union who are male and it distorts the figures.
"There is absolutely not a glass ceiling at the top of my union."