As the Tories turned their fire on Labour following Tuesday's manifesto launch, the Prime Minister claimed there was a £58 billion black hole in Mr Corbyn's plans - a figure rejected by Labour who insist the programme is fully costed - while Mr Hammond said numerous party's plans to nationalise industries and raise tax on the rich were "questionable".
The leaked manifesto suggested that Jeremy Corbyn's party would allow people to retire at different ages depending on the types of jobs they did during their working lives.
Critics say the manifesto evokes the party's 1983 offering, described then by a Labour lawmaker as "the longest suicide note in history" for helping the Conservatives win, and the ruling party questioned its funding plans.
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.
Promising "hope" to Britain's poorest, he attacked the ruling Conservative Party for increasing inequality since it took power in 2010.
Outlining pledges to nationalise water, energy, railways and the Royal Mail, Jeremy Corbyn took aim at Tory leader Theresa May.
On the planned increase in corporation tax, Helen Miller, an associate director at the Institute for Fiscal Studies (IFS), said, "A rate of 26% would, just, leave the United Kingdom with the lowest headline corporation tax rate in the G7".
The Institute for Fiscal Studies said Labour's proposal to increase income tax would raise a "highly uncertain" figure - and possibly nothing.
The manifesto says a Labour government would "immediately guarantee" existing rights for all European Union nationals in Britain and would "reject "no deal" as a viable option".
She argued that in Edinburgh South - the only Scottish seat won by Labour in the 2015 general election - it is Labour alone who can defeat the SNP.
The opposition party has also released a document revealing how their policies are being costed alongside the manifesto, saying that it will spend £48.6bn but bring in the same amount through mainly raising corporation tax and income tax for the top 5%.
"But, actually I think there's an terrible lot of uncertainty about whether you could actually raise that amount of tax".
There was confusion over whether Labour's manifesto was committing the party to ending the freeze on benefits.
The Tories have been sitting comfortably ahead of Labour in recent polls.
A policy promise his rival Theresa May has also made.
Labour is the most popular party among voters aged between 18 and 24, and a large part of its campaigning effort has been invested in encouraging members of the demographic to register to vote.
"Labour's manifesto-unveiled today-is a moderate, commonsense set of antidotes to the big problems holding back one of the wealthiest countries on earth", Jones wrote.
"But let me say this - over this next couple of weeks, if he's still there, I am challenging him to a televised debate".