The UK’s budget watchdog has called chancellor Rishi Sunak’s spending announcements the “largest budget giveaway since 1992” which will add more than £100bn to the public debt by 2024.

In the government’s first Budget since the Conservatives’ landslide election victory in December, chancellor Rishi Sunak announced a £30bn stimulus package to support the economy through the coronavirus outbreak and put the final nail in austerity’s coffin.

Read more: Budget 2020: Rishi Sunak pledges £30bn to ease coronavirus impact

The Office for Budget Responsibility (OBR) said the spending would take government borrowing to a six-year high of £66.7bn in 2021-22.

Among the key measures were a freeze on business rates payments for small firms for a year, and £3,000 grants for businesses that do not pay rates, costing the government roughly £3bn.

The dramatic spending increase came four years after then-chancellor George Osborne said the Tories would by this year turn the deficit into a surplus.

The OBR said that compared to its previous estimates, Sunak’s spending spree will increase the budget deficit by 0.9 per cent of GDP on average over the next five years and add £125 billion to the public debt by 2024-25.

The watchdog said UK GDP growth would fall to 1.1 per cent in 2020 from a prediction of 1.4 per cent growth a year ago. The OBR’s forecasts were prepared between 18 and 25 February.

However, the OBR said Sunak’s spending boost would push up GDP growth to 1.8 per cent in 2021, above the 1.6 per cent it had originally predicted.

Sarah Carlson, senior vice president at ratings agency Moody’s, said the fiscal stimulus “should help to support economic growth given the economic headwinds created by Covid-19”.

Read more: Budget 2020: Chancellor dodges fiscal rule change as borrowing rises

Yet she said it represented the Conservative government turning against any commitment to reducing public debt.

“The resulting deterioration in the UK’s fiscal position highlights the sovereign’s ongoing difficulty in meaningfully reducing the UK’s gross general government debt burden from its current high levels,” she said.