George Osborne has said the British government would lose £36bn in net tax receipts, equivalent to 8p on the basic rate of income tax or 7p on VAT, if the UK leaves the EU and negotiates a bilateral trade agreement with the bloc.

The chancellor said a 200-page Treasury analysis of the impact of Brexit showed it would make British families poorer, and he accused leave campaigners of believing that was a price worth paying. But out campaigners said that the chancellor was talking down the British economy in an unpatriotic way.

The study concluded that a Canadian-style model, in which the UK negotiated a new trade deal with the EU that did not require freedom of movement, would reduce Britain’s GDP by 6.2%.



“Under any alternative, we’d trade less, do less business and receive less investment, and the price would be paid by British families,” Osborne said. “Wages would be lower and prices would be higher.

“The most likely result is that Britain would be poorer by £4,300 per household. That is £4,300 worse off every year, a bill paid year after year by the working people of Britain.”

Osborne pointed out that a net loss of £36bn a year was the equivalent of a third of the annual budget for NHS England.



He said the study showed that whatever model Britain opted for after Brexit would result in significant barriers to the country’s most important export market, with 500 million consumers.

A Conservative minister said the analysis was unfair and biased, and argued that the government ought to provide both sides of the story if it wanted Britons to have a truly free vote. Andrea Leadsom, the energy minister, said remain supporters were talking down the economy in an unpatriotic way.

“This Treasury report is extraordinary,” she said. “For a start, it is only looking at one issue, which is their thesis on what happens if we leave. A Treasury report that is a genuine choice for the people should look at the impact if we remain.”

Howard Archer, economist at the consultancy IHS Global Insight, said nobody knew how the UK economy would fare post a Brexit-vote. He said that the “meaningful approach is to focus on the factors that will most influence how the UK economy will perform and to highlight the issues”.

He added: “To this end, the Treasury’s report does bring useful analysis to the table, and it steps up pressure on the campaigners for the UK to leave the EU to come up with more rigorous economic analysis that supports their case.”

The Treasury’s study is published as opinion polls point to an uncomfortably tight referendum for the chancellor and the prime minister. A new Guardian/ICM telephone poll, conducted over the weekend, puts remain on 54% and leave on 46% once the don’t knows are excluded.

In parallel, ICM released a second poll conducted online that points to a dead heat, with 50% of respondents plumping for remain, and 50% for leave.

Prof John Curtice calculates a weighted average of all published polls, and says the new data from ICM is very much in line with what he is seeing elsewhere. Remain had been running at around 54% overall in his series at the start of the year, and has now dropped to 51%, a figure that means “this referendum is now an awful lot closer than it was meant to be”.

The tightening, Curtice explains, is entirely explained by movement in telephone surveys. “Whereas internet polls have for months been suggesting a country that is split down the middle, until recently this was offset by the surveys done over the phone, which were recording a far higher share for Remain, sometimes approaching 60%”. But with the last few telephone polls, this proportion has dipped below 55%, a trend confirmed in Monday’s Guardian survey.

The government analysis also looked at the potential impact of a Norway-style model that would require freedom of movement, and signing up to a World Trade Organisation model.

It concluded that the WTO option would lead to a £45bn drop in tax receipts, and a 7.5% drop in GDP, a position Crabb described as extreme. Even the Norway model would mean a £20bn drop in receipts and a 3.8% hit to the economy.



Osborne said the EU was Britain’s most important trading partner, and that under the Norway model free movement would still have to be followed.

“We are not Canada,” he said, pointing out that the deal would not include services. He said British families would pay a heavy price and would be poorer if the UK left the EU.

Asked whether the government was abusing its power by producing the Treasury document, David Cameron’s official spokeswoman said: “In response to the debate in parliament as the EU referendum bill was being taken through in order to become an act, we committed to producing this.



“In the debate in parliament, which MPs and peers were involved in, a number expressed an interest in hearing more about the economic consequences of our membership and we committed then to doing this.”

Gisela Stuart, a Labour MP and chair of the Vote Leave campaign, called for the government to speed up the publication of a report on the impact of migration on school places, after allegations it was being delayed until after the referendum.

“I’m deeply concerned to hear of yet another example of the government seeking to sway the debate by hiding inconvenient facts from the British people,” she said. “This has become a clear pattern of behaviour, and it is ill befitting of a government that claims to want to have an open and honest debate.

“It is vital this report is released before the referendum so people can make an informed decision, and I urge Nicky Morgan to publish without further delay.”

The former chancellor Norman Lamont described the Treasury predictions as “spurious and entirely unbelievable”.

“They say economists put a decimal point in their forecasts to show that they have a sense of humour,” Lord Lamont said.

“The chancellor has endorsed a forecast which looks 14 years ahead and predicts a fall in GDP of less than 0.5% a year, well within the margin of error. Few forecasts are right for 14 months, let alone 14 years.”

Vote Leave, the leading out campaign, claimed that the £4,300 figure was based on the assumption that the government would break its promise of reducing net migration to the tens of thousands.



It claimed that if migration did fall there would be no additional cost for families, and said the Treasury had failed to account for savings from lower regulation if Britain were to leave the EU. It also accused officials of failing to look at potential benefits from trade deals with other non-EU countries.



Matthew Elliott, Vote Leave’s chief executive, said: “The headline figures in this report are deeply flawed. It is not credible to make these claims without showing your workings or the alternative you are comparing it to. It also ignores the Treasury’s own analysis that EU regulation costs the UK economy much more, a staggering £125bn a year.”

He said Britain was the fifth biggest economy in the world. “If we vote leave we will also be able to do deals with growing countries like China and India, which will help businesses to grow, create jobs and make our economy stronger.”

Another group, Grassroots Out, argued that the £4,300 figure amounted to 21p a person a day in return for national sovereignty.

For general election voting intention, ICM’s telephone poll puts the Conservatives on 38%, Labour on 33%, Ukip on 13%, the Lib Dems on 7%, the Scottish Nationalists on 5%, the Greens on 3% and Plaid Cymru on 1%.

Monday’s five-point lead for the Tories comes after a difficult couple of month for the government since the budget, and contrasts with some other recent polls, which actually put Labour ahead.

It is, however, in line with ICM’s online voting intentions, which the company publishes for the first time on Monday. These figures put the Conservatives on 36%, Labour on 31%, Ukip 16%, the Lib Dems 7%, the SNP 4%, the Greens 4%, Plaid Cymru 1% and others on 1%.