Brexit could lead to "decade of uncertainty", Whitehall report claims

The Whitehall report said the process of agreeing withdrawal and setting up new trade deals would rock financial markets, reduce investment, send the pound even lower and hit two million expats' pensions and healthcare.

"A vote to leave the EU would be the start, not the end, of a process. It could lead to up to a decade or more of uncertainty," the report, written by civil servants, said.

Campaigners for the Leave vote complained the report said the government was launching “Project Fear”.

London mayor Boris Johnson accused David Cameron and other Remain campaigners were only trying to "provoke only one emotion in the breast of the British public and that is fear...[and] quivering apprehension".

Johnson accused George Osborne's Treasury department of "talking up" threats to the economy by persuading G20 finance ministers to include a dramatic warning that Brexit would cause a "shock" to the global economy in a post-summit communique.

Monday's report detailed the lengthy process of withrdrawing from the EU, if such an event is chosen in the 23 June referendum, with unanimous agreement required from all 27 other EU countries, many of whom could push for concessions from Britain.

"The UK’s withdrawal from the EU would mean unravelling all the rights and obligations – from access to the single market, to structural funds for poorer regions, to joint action on sanctions – that the UK has acquired both during our accession to the EU and over our 40-year membership.

"As well as negotiating its withdrawal, the UK would also want to negotiate its post-exit arrangements with the EU,” the civil servants maintained.