Sajid Javid and John McDonnell could go head-to-head in a television debate amid a row over Labour’s reported £1.2 trillion in spending promises.
The Conservatives have published a dossier which Mr Javid said showed the “true cost of Corbyn”, including taxes set at the “highest level we’ve ever seen in peacetime”.
The Chancellor went further yesterday, warning that Labour will lead the UK into economic crisis “within months, not years”.
Mr Javid said he is ready to face Mr McDonnell in a live debate. It is understood shadow Chancellor yesterday said he has agreed to appear in debates proposed by two broadcasters.
However sources said Number 10 have held up the debate. Channel 4 is the only mainstream channel to have made a bid. The Daily Telegraph understands that Downing Street’s communications chief was “furious” with Channel 4 after comments made by its head of news, Dorothy Byrne.
Ms Byrne described Boris Johnson a "known liar" and a "coward" at an event in August. Relations with Channel 4 are believed to have been “in the cooler” since the comments.
In 2010 Channel 4 hosted the first Chancellors' debate, where Alistair Darling, George Osborne and Vince Cable took part in an hour long special.
It came as the election battle lines were increasingly drawn over the two parties’ spending plans. Mr Javid said Jeremy Corbyn was promising an “eye-watering level of spending”, calling his policies “reckless”.
Speaking on the BBC’s Andrew Marr Show, the Chancellor said: "This is the true cost of Corbyn's Labour: these are the numbers that John McDonnell did not want you to see, and they're out there today.
"It will be absolutely reckless and will leave this country with an economic crisis within months, not years."
Mr Javid would not be drawn on details of his own spending plans and said the Conservatives would set them out during the course of the campaign. However he said the policies are “properly costed”.
The Conservative party will finalise its manifesto “in the next two weeks”, a source said. Domestic policy pledges expected this week include announcements on immigration and education.
The Chancellor said: “Whether it's a tax pledge or anything else, we will be clear about how we will be funding that and that will be absolutely inside our fiscal rules.”
Mr Javid said Labour's proposals - which include plans to renationalise rail, mail, water and energy - would "undo all the hard work of the British people in recent years" and leave the economy on the "brink of bankruptcy".
However, Mr McDonnell branded Mr Javid's claims "fake news" and called the report "an incompetent mish-mash of debunked estimates and bad maths".
He said: “Labour will tax the rich to pay for things everyone needs and deserves, like decent housing, healthcare and support for our children.
“The Conservatives will be able to read all about these plans – and how much they actually cost – when we publish our fully costed manifesto."
Business minister Kwasi Kwarteng also warned of the “reckless and unaffordable” spending of the Labour Party.
“We can’t have politicians going round promising the Earth,” he said.
However, Mr Kwarteng repeatedly denied to give costings for the Tories own policies.
"I'm not going to bandy around figures," he said.
"It's absolutely right for us to say this is what the opposition are saying and this is how much it is going to cost."
The Tories’ £1.2 trillion figure comes from a 36-page document, drawn up by the Conservative Research Department, after the shadow chancellor objected to plans for the Treasury to publish an analysis of his fiscal plans last week.
The analysis claims the party is committed to spending £650 million a day, which the Chancellor claimed was the “equivalent of scrapping all funding for the NHS for the next nine years”.
It also assumes Labour would immediately sign up to the 32-hour week, abolish private schools, and pilot a universal basic income. Nia Griffith , the shadow defence secretary, yesterday challenged the claims and said Labour would not implement every policy from its annual conference - as the party could "only do a certain amount at once".
Shadow Cabinet minister Andrew Gwynne said the figure is “an absolute work of fiction by the Conservatives”
The shadow secretary for communities and local government said: "We will have a fully-costed manifesto in due course when we launch that, and the challenge actually is for the Conservatives to fully cost their own manifesto, something they didn't do in 2017."
Mr Gwynne also revealed Labour will finalise its manifesto on Saturday, which he said would be “fully costed”.
He said: “We don’t know what the manifesto is going to be in its entirety” and pointed out the total cost of spending is “still being finalised".
“Next Saturday we’ve got our Clause V meeting where the whole Labour family, the shadow cabinet, the trade unions, affiliated organisations and the national policy forum all come together.
He added: “There will be open transparency from the Labour party. Let’s see that from the Tories.”