Civil servants have been warned that they must make the patriotic case for Brexit amid concerns it is increasingly viewed as a “risk” by the public.

A Cabinet Office paper said that evidence from focus groups highlighted the need to “change the language” around Brexit in a bid to build public trust.

The paper, discussed by senior civil servants in early December, raised concerns that the public are increasingly “nervous” about the prospect of Britain leaving the European Union.

Last week Sir Ivan Rogers, Britain’s top official in Brussels, quit, urging other civil servants to “to challenge ill-founded arguments and muddled thinking” about leaving the EU.