Mr McCluskey said those “anti-Corbyn” figures were trying to “stick Rebecca” with the same criticism, adding: “She is an individual completely different from Jeremy Corbyn.”
But, asked to identify a policy area where they differed, he told the BBC’s Andrew Marr Show to “ask her”, insisting: “She will have her different views on what her priorities are.”
The comments came as Mr McCluskey again turned on Corbyn critics – including the Jewish Labour Movement – for “using” the antisemitism controversy to “undermine” the outgoing leader.
And he repeated his claim that Brexit divisions and confusion – not Mr Corbyn’s unpopularity – led to the party’s general election disaster.
“Two years ago Jeremy Corbyn was loved,” Mr McCluskey claimed.
“What happened in the last two years? Brexit, and Labour’s inability to effectively stay with their 2017 manifesto position of respecting the 2016 referendum and arguing to take Labour and the country out of Europe on a deal that protects jobs and investment.”
Keir Starmer, the shadow Brexit secretary who will return to the leadership race on Monday after a family accident, is the favourite to win when the result is declared on 4 April.
The battle to replace Jeremy Corbyn as Labour leader
Show all 8
However, Ms Long-Bailey remains his strongest rival with the backing of the left-wing group Momentum as well as Unite.
But Mr McCluskey said criticism that she would carry Corbyn’s torch was “unfair”, adding: “People will see she’s strong, courageous, brave, certainly capable and she’s able to take forward her vision.”
He dismissed suggestions that Richard Burgon and Dawn Butler should be ruled out of the deputy leadership contest if they do not sign up to the Board of Deputies‘ 10 pledges to “end the antisemitism crisis”,
“They believe there’s a need for more debate and discussion about a couple of the points that are in the Board of Deputies pledges – most of them are fine but a couple of them need further consideration.
“For people to call for them to be kicked out of the race is utter nonsense.”
Mr McCluskey said Labour “never handled the antisemitism issue correctly”, but alleged some of the leader’s opponents had been “quite despicable” in using it “undermine Corbyn”, saying: “There’s no doubt about that.”
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies