Earlier today Labour's manifesto was condemned as a "fantasy wishlist" by Prime Minister Theresa May.
Theresa May was confronted by a fan of Jeremy Corbyn's manifesto as she took calls from the public in a "telephone town hall" event.
The party also plans a levy on businesses with staff earning large salaries over £330,000.
McCluskey's analysis, made in an interview with the Politico website, was widely seen as an attempt to lower expectations, in order to prepare to make an argument for Corbyn to remain as Labour leader even if he suffers a heavy election defeat. However, Labour did not provide detailed costs for a plan to nationalise railways, the Royal Mail and parts of the energy industry.
Len McCluskey, the head of the union Unite, which is Labour's biggest funder, said on Wednesday he was "full of optimism" about the party's chances in the 8 June poll.
The final version will form the foundation of Labour's pitch to voters in the June 8 snap general election.
"No one should believe false Tory claims that they are the workers party". In the main, that contribution will come from dropping the threshold for the additional rate of income tax (45%) from £150,000 to £80,000 while those with earnings over (a very precise) £123,000 paying tax at a [re-introduced] 50% rate.
"I think there's a rumbling, a subterranean rumbling at the moment, where people are saying we want change".More news: Australian banks lick wounds after tax hit
There was confusion over whether Labour's manifesto was committing the party to ending the freeze on benefits.
Chancellor Philip Hammond said: "There is a £58 billion black hole in Jeremy Corbyn's manifesto - and it will be paid for by every single family in the country with higher taxes and more debt".
But writer Barnaby Neale, a Labour volunteer, said the "inspiring" manifesto would sway voters.
Kezia Dugdale has rejected the view of union boss Len McCluskey, who said he can not see Labour winning the General Election.
The General Election could determine if the United Kingdom continues to exist, Kezia Dugdale warned, as she urged people in Scotland to reject the nationalist politics offered by the SNP and the Conservatives.
We're not going to repeat them here, but suffice to say the report is extremely slanted in a direction that we honestly struggle to recognise following years of following JME's work (and social media output).
"Tax burden already heading upwards".
The IFS said: "The tax revenue that Labour's proposal would raise is highly uncertain".