A vote to leave the European Union on June 23 would push the United Kingdom deeper into economic despair, which would force the country’s finance ministers to extend austerity measures for two more years, the Institute for Fiscal Studies recently warned.

The London-based think tank, which has been lauded for its fierce independent over the past 47 years, has stated that Brexit would cost the public purse between £20 billion and £40 billion in 2019-2020, which more than offsets the Conservatives’ planned surplus.

“[T]here is an overwhelming consensus among those who have made estimates of the consequences of Brexit for national income that it would reduce national income in both the short and long runs. The economic reasons for this – increased uncertainty, higher costs of trade and reduced FDI – are clear,” the Institute for Fiscal Studies (IFS) said in a report published on May 25.

As a result, up to two additional years of austerity, which includes a combination of spending cuts and tax increases, would be required to re-balance public finances. The IFS added that even the most optimistic forecasts do not see Britain compensating for the loss of foreign investment and overseas trade that would result from leaving the EU.

Carl Emmerson, IFS deputy director and co-author of the report, added that, “[The] overwhelming weight of analysis suggests that the economy would shrink by more than enough to offset the positive effect on the public finances of the reduced financial contribution to the EU budget.”

The IFS findings are in line with a broad view of economists and market analysts who anticipate a severe backlash for the UK economy in the event of a Brexit. The World Trade Organisation (WTO) and Group of Seven advanced economies have also issued warnings about the economic consequences of Brexit.

The G7 wrapped up its two-day summit in Japan on Friday, but not before issuing a grave warning on Britain’s upcoming referendum.

“A UK exit from the EU would reverse the trend towards greater global trade and investment, and the jobs they create and is a further serious risk to growth,” the G7 said in a 32-page declaration that tackled everything from weak economic growth to geopolitics.

Analysts have described the IFS report as a major blow to the Vote Leave campaign, which is playing catch up to the Remain camp. According to the Telegraph’s poll of polls tracker, 54% of Brits are planning on voting “Remain” next month compared with 46% who will vote “Leave.” Both sides were essentially 50-50 just a few weeks ago.

It did not take long for Vote Leave to launch a rebuttal to the IFS report. UKIP leader Nigel Farage was quick to point out that the London-based think-tank receives a portion of its funding from the European Union. The Vote Leave campaign dismissed the report as “paid-up propaganda.”

British Prime Minister David Cameron was just as quick to praise the IFS, referring to it as the “independent gold standard.” Mr Cameron has a long month ahead trying to convince the public and members of his own Cabinet about remaining in the EU.

The potential of an economic shock following a Brexit vote is no doubt on the mind of British voters, who have seen their economy slow in recent quarters. Gross domestic product, the value of all goods and services produced in the economy, expanded just 0.4% in the January-March period, the slowest expansion since the third quarter of last year.

According to analysts, much of the initial impact to the UK economy will result from higher borrowing costs as Britain’s debt rating is downgraded. This will likely be accompanied by a loss of confidence among international investors. This could potentially unwind Britain’s property market, especially in London, which attracts a great deal of foreign investment.

The National Institute for Economic and Social Research (NIESR), a London-based think-tank, judges that the immigration reforms associated with Brexit will also limit economic growth. NIESR forecast data formed the basis of the IFS report that was released last week.

Bank of England (BOE) Governor Mark Carney recently said that the central bank could comment on the referendum debate on June 16 when it releases the minutes of its last policy meeting. The minutes will be released just one week before the referendum vote.

The BOE has already expressed concerns about Brexit, acknowledging that a vote to quit the EU could result in an extended period of economic and financial instability. The British pound could be one of the biggest casualties, the Bank notes, as Brexit could force policymakers to slash interest rates from their current record low of 0.5%. The Bank’s Monetary Policy Committee has remained on the sidelines since the last recession.

The next three weeks could be especially volatile for the British pound and other UK assets. There’s no way to predict with certainty just what might happen should Brits vote out of the EU. According to most analysts, the referendum will be a nail-biter, but is unlikely to result in Britain quitting the EU. Only time will tell if they are right.

If you have an opinion about whether a Brexit will happen, then you can trade it with easyMarkets.