It has stressed that the new trading relationship between the UK and the EU will reduce long-run productivity by four per cent relative to remaining in the European bloc.
Both exports and imports will be around 15 per cent lower in the long run than if the UK had remained in the EU, it added.
Other economists have warned of multi-billion pound blows to Britain’s trade, a slump in investment, and some sectors such as hospitality are struggling to recruit enough workers with less migration from the EU.
Leading pollster Professor Sir John Curtice, from the University of Strathclyde, said voters had become “more pessimistic about the economic consequences of Brexit”.
He pointed to a shift in polls over the past three years with 58 per cent saying they would vote to join the EU when presented with a binary choice and 42 per cent backing remaining outside the bloc.
The PM’s upbeat analysis contrasted with the recent polling suggesting growing unhappiness with the way Brexit has turned out.
Mr Sunak said: “In the three years since leaving the EU, we’ve made huge strides in harnessing the freedoms unlocked by Brexit to tackle generational challenges.
“Whether leading Europe’s fastest vaccine rollout, striking trade deals with over 70 countries or taking back control of our borders, we’ve forged a path as an independent nation with confidence.”
A poll published by Ipsos on Monday found 45 per cent thought Brexit was going worse than they expected, up sharply from 28 per cent in June 2021, including just over one in four (26 per cent) of those who voted Leave in the 2016 referendum.
