Almost twice as many voters now believe Brexit is having a negative effect on the UK economy as think it is benefiting the nation’s finances, according to the latest Opinium poll for the Observer, carried out during budget week.

The survey comes after Richard Hughes, the chairman of the Office for Budget Responsibility, said his organisation calculated that the negative impact on GDP caused by the UK’s exit from the EU was expected to be twice as great as that resulting from the pandemic.

Hughes said Brexit would reduce the UK’s potential GDP by about 4% in the long term, while the pandemic would cut it “by a further 2%”. “In the long term, it is the case that Brexit has a bigger impact than the pandemic,” he said.

Opinium’s findings appear to be in line with other recent polling, including a survey last week by Ipsos MORI, which showed concern about the effects of Brexit rising to the point that it is now seen as the biggest issue for the country alongside Covid-19.

The Opinium survey found that 44% of people think Brexit is having a bad impact on the UK economy, compared with 25% who think it is having a positive effect.

More starkly, 53% of people believe Brexit is having a bad effect on prices in shops, against 13% who think it is having a good effect, while 51% think it is adversely affecting the UK’s ability to import goods from the EU, against 15% who think it is helping.

While chancellor Rishi Sunak‘s approval rating rose slightly after his Budget speech on Wednesday, in which he increased government spending to its highest sustained level since the 1970s while warning that inflation would rise to 4% next year, the fact that people appear to be linking Brexit with economic problems including rising prices will be a worry to No 10 and No 11 Downing Street.

During the campaign for Brexit, led by Boris Johnson and Michael Gove, voters were told by the Leave campaign that leaving the EU would create a more dynamic UK economy able to trade freely across the globe, and less bureaucracy, leading to lower prices.

The OBR report, published alongside Sunak’s budget, said that its evidence to date suggested its previous forecasts that Brexit would lead to a 15% fall in both UK imports from, and exports to, the EU appeared to have been broadly accurate.

The report said: “The evidence so far suggests that both import and export intensity have been reduced by Brexit, with developments still consistent with our initial assumption of a 15% reduction in each.”

It is also made clear that shortages of lorry drivers were at least partly caused by Brexit.

Last week the Financial Times reported that whereas by August this year global goods trade had rebounded sharply since the height of the pandemic (according to the CPB World Trade Monitor), the UK was proving a notable exception, with its exports still sharply down.

Since the end of the Brexit transition period on 1 January this year, UK ministers have insisted that difficulties with trade to and from the EU would be short-lived and amounted merely to “teething problems” that would be resolved quickly once companies got used to the new arrangements.

While Opinium found evidence of clear anxiety about Brexit, this has yet to translate into a negative effect on support for the Tory party.

The Conservatives are on 40%, down 1 point compared with a fortnight ago, while Labour is down 2 points on 35%. The Lib Dems are on 8%, the Green party 7%, the SNP 5% and Plaid Cymru 1%.