Chancellor Sajid Javid unveiled a dossier setting out the eye-watering price tag, claiming it represented the “true cost of Labour”.
However, the figures include proposals adopted at Labour conference which have yet to appear in a party manifesto - such as abolishing all private schools and making the UK carbon-neutral by 2030 - and also assume that policies like moving to a four-day week would be delivered on day one of a Labour government.
Shadow chancellor John McDonnell said the claims were a "ludicrous piece of Tory fake news" and an "incompetent mish-mash of debunked estimates and bad maths cooked up because they know Labour's plans for real change are popular".
Mr Gwynne revealed that Labour’s national executive will meet on Saturday to sign off the party’s manifesto.
Mr McDonnel insisted that the plans would be “fully costed”, adding: "Labour will tax the rich to pay for things everyone needs and deserves, like decent housing, healthcare and support for our children.”
The Chancellor said Labour's proposals - which include plans to renationalise rail, mail, water and energy - would plunge the UK into an economic crisis "within months".
"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,” Mr Javid told the BBC’s Andrew Marr Show.
"It will be absolutely reckless and will leave this country with an economic crisis within months, not years."
"I'm not going to bandy around figures,” Mr Kwarteng said.
Ms Griffith said Labour would not implement every policy from its annual conference - as the party could "only do a certain amount at once".