The British economy will suffer no matter what trade deal is struck with the European Union, according to leaked confidential report that was prepared for the British government. In the worst-case scenario, growth could fall 8% over a 15-year period.

According to reports in the media, the leaked report, which is titled “EU Exit Analysis – Cross Whitehall Briefing” and dated January 2018, also suggests all UK industries will be hurt by leaving the European Union.

As reported by Deutsche Welle (DW), Germany’s international broadcaster, the findings are the latest embarrassment for British Prime Minister Theresa May‘s government, which has faced renewed criticism from other EU leaders about the lack of a coherent Brexit strategy.

In the best probable case outlined in the leaked report, Britain remains in the EU single market. However, as a non-member of the bloc, decline would be 2%.

If the UK was able to agree a comprehensive trade deal with the EU, but remain outside the single market and customs union, growth would be 5% lower than current forecasts.

New British trade deals with the US, China, India and other countries would boost growth, but not enough to make up for the lost EU revenue, according to the report.

According to DW, the report is the latest to predict a major downturn in the British economy when the country completes its divorce process.

Asked about the report, a department spokesperson said: “We have been clear that we are not prepared to provide a running commentary on any aspect of this ongoing internal work”.

Asked by Buzzfeed News why the report was not being made public, the source answered: “Because it’s embarrassing.”

On January 30, several British lawmakers called on the government to release its impact report. Chuka Umunna, Labour MP and chair of the Brexit watchdog group Leave Watch, accused the government of failing to protect the British people’s interests by withholding the impact report.

In parliament, Brexit minister Steve Baker described the report was a “selective interpretation of a preliminary analysis” that had been leaked “to undermine our exit from the European Union”.

Baker also urged lawmakers to be cautious as many previous Brexit analyses had so far been proved wrong.

According to DW, the report heightens the deep uncertainty that followed the June 2016 decision to leave the EU. In the months after, the British pound fell sharply against the dollar and euro, and while the UK economy grew 0.5% in the final three months of 2017, annual economic growth was at the weakest rate since 2012 at 1.8%.