Hollywood legend Danny DeVito has backed Jeremy Corbyn as Britain's next Prime Minister. "I think it would be extraordinary", McCluskey was quoted as saying.
Following the launch of Labour's General Election manifesto on Tuesday, the Tories issued an analysis highlighting what it said were billions of pounds of unfunded commitments.
"They make it clear they don't want Jeremy Corbyn".
Mr Corbyn appears to have benefited from publicity over his far Left manifesto at the expense of the Lib Dems who have seen support collapse by 6 points to just 7 per cent.
The Scottish Labour leader called on voters to "reject the extremes of both the SNP and the Tories" and instead to back her party to help bring about "progressive change" in the country.
Shadow chancellor John McDonnell, speaking to supporters at a General Election campaign event in Lincoln, said: "We've got a lot of work to do, we know the polls at the moment, we know what they're like".
Mr Watson, Labour MP for West Bromwich East, said families were facing increases in food and energy bills under the Tories.More news: Zidane calm with Real Madrid one point away from title
More news: Enda Kenny resigns as Irish Fine Gael party chief
More news: Len McCluskey 'confident' that opinion polls will start to turn for Labour
If Labour were to win 200 seats, that would represent its worst result since 1935.
"And I just say this too: this could be a young person's election because large numbers of young people are registering; for the first time those interested in politics want to have their say".
Jeremy Corbyn and his team will take comfort in the poll, which suggests that the Labour vote is solidifying as the campaign advances.
The actor, producer and director - who shot to fame with his role in TV's Taxi and classic drama One Flew Over the Cuckoo's Nest - said the United Kingdom has "got the guy".
Scottish Labour believes that together we're stronger.
Mr McCluskey said it was hard for the party to challenge now only two years after losing an election and one year after Labour MPs attempted to replace Mr Corbyn as leader, a move he said gave the impression of a divided party in the minds of many voters.