A spending row has broken out after the Conservative Party published what it claims would be the cost of a Labour government over five years.
The report, compiled by the party and not the Treasury, is based on a number of commitments from Labour's annual party conference but not its manifesto.
Chancellor Sajid Javid said Labour's proposals would leave the UK "on the brink of bankruptcy".
But shadow chancellor John McDonnell condemned the report as "fake news".
The Conservatives claim that Labour's policies would cost £1.2tn over the course of the next five years, if the party wins next month's general election.
The figure is based on costing Labour's 2017 manifesto and other pledges it has made since then.
But the Labour Party has yet to publish its 2019 election manifesto, detailing its policies and spending proposals.
Senior Labour figures will meet next weekend to decide which policies passed by the party's annual conference will become manifesto proposals for government, with some unlikely to be confirmed.
Labour's shadow communities secretary Andrew Gwynne said the manifesto would be "fully costed" when it is published.
Challenged on the assessment by the BBC's Andrew Marr, Mr Javid stood by the figures.
He told the programme: "This is the true cost of Corbyn's Labour. These are the numbers that John McDonnell did not want you to see."
The chancellor added: "Of course [Labour] aren't going to welcome these numbers. They don't want to see this kind of transparency.
"These are eye-watering levels of spending… it will be absolutely reckless and will leave this country with an economic crisis within months."
But asked about the Conservatives' own spending pledges - and how they would be funded - Mr Javid only said the party would "set out our plans during the course of the election campaign".
"Our plans are properly costed and it will be clear how we will be funding that," he added.
Earlier, business minister Kwasi Kwarteng was pushed for the Conservatives' spending plans by Sky News' Sophy Ridge programme, but he said he was "not going to bandy around figures".
"I'm not going to bandy around figures."— Sophy Ridge on Sunday (@RidgeOnSunday) November 10, 2019
Business Minister @KwasiKwarteng says Labour's spending plans are "reckless and unaffordable".
But he won't say how much Conservative spending plans add up to.
Follow #Ridge live 👉 https://t.co/qplpD1wUuK pic.twitter.com/orNVEXI7FX
Mr McDonnell branded the Conservative report 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".
And Mr Gwynne told the BBC's Andrew Marr show the Conservative claims about Labour spending were "an absolute work of fiction".
The shadow minister said his party's proposals would be "open and transparent" on costings, and called on the Tories to do the same with their manifesto.
Neither the Conservatives nor Labour have confirmed a date for when their manifestos will be published.
But the deputy leader of the Liberal Democrats, Ed Davey, has called for both parties to submit their manifestos to the Office for Budget Responsibility to be independently costed.
"The cash commitments that are being thrown around by the two old parties need to be subject to proper scrutiny," he said.
"Manifestos need to be independently assessed and costed by the Office for Budget Responsibility so that the public can be confident that flagship policies can be delivered."
Mr Davey said the Lib Dems were "more than prepared" to do the same with their own manifesto when it is published.
How accurate are the claims?
There are problems with the Conservative Party's approach.
As Labour has not yet published its election manifesto, previous pledges may well be dropped, while new ones could still be added.
That makes the job of accurately costing election pledges, at this stage of the campaign, impossible.
Just because certain policy positions passed at the Labour conference, there is no guarantee they will be adopted in the upcoming manifesto.
There is also an issue with some of the costing. For example, the Conservatives cost Labour's renationalisation plans at £196bn. This is based on a Confederation of British Industry estimate, which was itself the subject of criticism.
But it is certainly true that Labour wants to spend a lot more - something it has been upfront about.
Shadow chancellor John McDonnell says he wants to more than double UK investment spending to an extra £55bn a year.
However, the Institute for Fiscal Studies has called into question where such an immediate increase in investment spending could be achieved.
The publication of the Conservative document comes after civil service head Sir Mark Sedwill blocked a Tory plan to use civil servants to cost the Labour Party's fiscal plans in a separate report.
Sir Mark's decision came after Mr McDonnell complained vociferously to Treasury Permanent Secretary Tom Scholar.
Speaking about Labour's plans in Liverpool on Thursday, Mr McDonnell promised "investment on a scale never seen before" to overhaul infrastructure in all areas of the UK.
The shadow chancellor said he wanted to transfer power and money out of the south-east of England - and will fund his plans through borrowing.
He said his party would introduce new fiscal rules, meaning "borrowing for investment" would not be included in borrowing targets.
Labour's economic plan includes doubling "investment" spending, a £150bn "social transformation fund", and a £250bn "green transformation fund".
The Tories have also vowed to borrow to fund more spending, rewriting their current financial rules.
'A political document'
This document is political rather than financial. The Conservatives' aim is to frame Labour's plans not as ambitious, but as unaffordable.
But the dossier assumes that all Labour's policies are firm commitments, and it does not examine Labour's revenue raising measures.
John McDonnell has made no secret that Labour intends to borrow more than the Tories to invest - his political argument is that this would both grow the economy more rapidly and increase the state's assets - not just its liabilities.
So, in the end, the calculation voters are likely to make is about who they trust more to run the economy.
Do you have any questions about the general election?
In some cases your question will be published, displaying your name and location as you provide it, unless you state otherwise. Your contact details will never be published. Please ensure you have read the terms and conditions.
Use this form to ask your question: