Published: 10:51 AM July 25, 2018 Updated: 6:21 PM September 17, 2020

People who "undermine" the UK 'through extreme EU loyalty' should be tried for treason, a hardline Tory MEP has demanded.

David Campbell Bannerman, a former Ukip deputy leader, made the astonishing call for thoughtcrimes to be prosecuted on Twitter, sparking accusations of "spiteful populist rhetoric".

He wrote: 'It is about time we brought the Treason Act (of 1372) up to date and made it apply to those seeking to destroy or undermine the British state.

'That means extreme jihadis. It also means those undermining the UK through extreme EU loyalty.'

He later deleted the tweet, only to tone it down as: 'It also means those in future actively working undemocratically against UK through extreme EU loyalty.'

It is about time we brought the Treason Act up to date and made it apply to those seeking to destroy or undermine the British state. That means extreme jihadis. It also means those in future actively working undemocratically against U.K. through extreme EU loyalty pic.twitter.com/CXSPCJqjOz

-- David C Bannerman (@DCBMEP) July 25, 2018

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The Tory MEP for the east of England was referring to the front page of today's Daily Telegraph, which reports calls from the think-tank Policy Exchange for treason laws to be updated and used to prosecute jihadists who have fought in Syria.

Labour MP Virendra Sharma, a champion of the Best for Britain group which is campaigning for a second referendum, said: "This C-list Tory MEP is suggesting putting the knife into free speech.

"One of the best things about this country is the range of opinions that help diversify our political debate. David Bannerman should think long and hard about his spiteful populist rhetoric.

"This type of extremism is the real danger facing this country."

The Treason Act 1351 remains in force in the UK, but no longer provides secure ground for prosecuting terrorists who conspire to attack the UK, Policy Exchange has said.

Its report itself does not mention the EU, although its introduction mentions 'taking one's primary loyalty to be to some other political arrangement or cause'

The last person to be prosecuted for treason – which covers the most extreme crimes against the state – in the UK was William Joyce, nicknamed Lord Haw-Haw, who was executed in 1946 for his pro-Nazi broadcasts.