The Treasury is set to borrow another £50bn in August as it races ahead with a record debt spree to fight the coronavirus crisis and plug a collapse in tax revenues.
It means borrowing will hit £275bn in the opening five months of the financial year - an unprecedented pace to match the extraordinary strains on the public finances as the country reels from the biggest challenge since the Second World War. The figures will spark concern that Britain will be paying for the crisis for years to come through higher taxes.
Economists had expected the state-run Debt Management Office (DMO) to set out plans for September too, but it decided not to amid a rapidly changing situation with economists unable to predict the scale or speed of any recovery.
The nation's debts are rocketing after Chancellor Rishi Sunak unveiled a historic package of state support to protect jobs from the ravages of the coronavirus lockdown.
Big contributors to the extra deficit include the furlough scheme, which the Office for Budget Responsibility estimates will cost £60bn; support for the self-employed totalling £15bn; the same amount again in business grants; almost £12bn of cuts to business rates; and an extra £16bn on public services such as healthcare.
Funding for another £40bn of taxpayer-guaranteed loans is not included in the estimates, with their final cost to the Exchequer likely to stretch out for years to come.
Jacob Nell, economist at Morgan Stanley, expects more stimulus from Mr Sunak in the form of tax cuts and spending increases - with even more borrowing as a result. He is predicting stimulus equal to 3pc of GDP, with a focus on investment as well as modest tax cuts such as on employers' national insurance contributions. Mr Nell does not expect a VAT cut after the proposal was downplayed by Treasury sources.
Boris Johnson is expected to launch a £1.5bn school-building blitz to boost the economy after lockdown, and will on Tuesday set out other infrastructure projects including details of 40 new hospitals which have already been promised alongside major spending on housing, roads, railways and prisons.
The Government is already on course for the biggest deficit in peacetime history.
Mr Nell predicts borrowing will close in on 16pc of GDP this year - far in excess of the nearly 10pc peak in the financial crisis.
As ministers must also issue bonds to refinance old debts as they come due, this means the DMO will have to raise about £420bn this year.
Morgan Stanley expects the Bank of England to add another £100bn to its money-printing programme later in 2020, meaning the central bank will absorb £400bn of bonds in the secondary market - close to matching all gross issuance by the DMO.
Bank officials have denied they are taking part in so-called monetary financing, a policy associated with hyperinflation in Zimbabwe and 1930s Germany where new cash is created solely to fund state debt.
The scale of the economic shock is such that the Government will borrow heavily for some time to come.
Economists expect public borrowing to remain at about £155bn next year, according to private forecasts collated by the Treasury.