The increase in public spending outlined in the Budget will leave the UK's economy "vulnerable" due to increased borrowing costs, according to the Office for Budget Responsibility (OBR).
Yesterday, the Chancellor Rishi Sunak announced tens of billions of extra spending to help tackle Coronavirus and support small businesses, funded by increase borrowing.
The OBR warned that abandoning the government's plan to balance the books in the long-term could be affected by such an increase in short-term spending.
Sir Charlie Bean, a member of the OBR's budget responsibility committee, added: "Clearly the more debt you build up, the more exposed you are if things go wrong.
"And there's a good general principle that you want to have the debt-to-GDP ratio declining in good times, to build up the space for responding precisely to the events like the coronavirus.
"If you only have the ambition to keep debt constant as a proportion of GDP, every time you get a bad shock, you just ratchet that up again."
The OBR downgraded its economic growth forecast for 2020 as part of the Budget statement, but Mr Sunak explained that the forecast did not take into account the anticipated impact of the Coronavirus.
The Chancellor today (Thursday) defended the extra spending and borrowing detailed in the Budget, insisting it was "the right economic thing to do"