Pulling out of the European Convention on Human Rights would not betray the legacy of Sir Winston Churchill, according to a new report backed by a former Supreme Court Justice and the author of a landmark biography of the wartime Prime Minister.

Last year Sir Keir Starmer told European leaders gathered at Blenheim Palace – the birthplace of the late PM – that the UK will “never withdraw from the European Convention on Human Rights”, declaring that “Churchill himself was among the chief architects of the Convention”.

But historian Lord Roberts, writing in the foreword to a new Policy Exchange paper, claims it is “groundless” to charge “Tories who flirt with ECHR withdrawal” of betraying Churchill’s legacy.

He writes: “Invoking the memory of Churchill to support the ECHR, or to oppose UK withdrawal from it, is either base opportunism or basic historical misunderstanding. The historical record matters and the memory of Churchill should not be weaponised for political advantage, not least in service of a cause that he would have viewed as wholly incompatible with parliamentary democracy and the prerogatives of the nation state.”

Lord Roberts, the author of Churchill: Walking With Destiny, adds: “He was responsible neither for the drafting of the ECHR nor the UK’s adoption of it, which fell instead to the Attlee Government, which harboured grave doubts about the wisdom of entry into the Convention and did its best to limit its scope. When back in power, Churchill showed no interest whatsoever in the ECHR, clearly sharing the view of the Labour government that Britain was in no need of further human rights protection.”

Former Supreme Court Justice Lord Sumption also challenges the idea that the present system around the enforcement of the Convention is a British creation.

He writes: “The current Convention system is essentially the creation of the European Court of Human Rights in Strasbourg. Neither the Atlee government, nor the Churchill government which succeeded it in 1951, nor the lawyers, officials and politicians involved in negotiating the treaty wanted to see it enforceable by a supranational court. They thought that this would infringe the sovereignty of the United Kingdom in ways which were inconsistent with its Parliamentary democracy.”

Lord Sumption argues the Convention is “no longer recognisable as the instrument which British negotiators and draftsmen envisaged” in the aftermath of World War II.

He adds: “Half a century later, it has now became an expanding source of domestic law over which Parliament has no influence or control and which it cannot repeal or amend. The British electorate has no input into it.”

A Reform UK spokesman responded to the paper, saying: “It’s clear that remaining in the ECHR does not serve the interests of the British public and is a threat to our sovereignty. The British people alone deserve to be the ultimate arbiters of our own country, borders and laws.

“The notion that leaving the ECHR would destroy British legacy is absurd. Instead, it would allow the people to take back control of our legacy and values.

“Using Sir Winston Churchill’s memory to push this agenda is an insult to his memory.”

The Government was invited to comment.