Then foreign secretary Douglas Hurd sent a “parting shot” to John Major upon leaving office outlining the need to remain within the European Union, new documents reveal.

Confidential papers sent to the then prime minister in 1995, entitled The Hurd Legacy: Enhancing The Overseas Effort, describe how Britain remains “a major country in the world” but that there is “a need to practise polygamy”.

Mr Hurd urged Mr Major to grant “modest but reasonable” expansion of its embassies and the number of diplomats, to “polish” the jewels in the British crown – such as the BBC World Service – and to stem any proposed cuts to defence budgets.

A document containing a precis of Mr Hurd’s thoughts, released by the National Archives, describes the importance of its close relationship with Europe.

It adds: “As a medium-sized power in a world lacking an effective superpower, we can best pursue our interests through multilateral organisations, buttressed by selected bilateral alliances.

“The European Union is the most important. But we have a strong interest in others as well.

“The common interests of Europe, the growing threats of drugs, crime and immigration, the economic interdependence, means that the European Union has to keep on moving forward.

“We could not make Europe stand still, and it is not in our long-term interests to do so.”

Mr Hurd said feelings towards Europe in the UK were “poisonous”, “(tipping) over into xenophobia”.

He added: “The world and our interests in it are too complex for us to rely on a single partner – we need to practise polygamy.”

Britain voted to leave the EU on June 23 2016.