Longstanding Leave campaigner David Campbell Bannerman, who is also a former UKip deputy leader, made his comment in a Tweet which reflects growing public anger at the way some leading Remainers have taken the side of Brussels in the Brexit negotiations.
Mr Campbell Bannerman Tweeted: “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 UK through extreme EU loyalty.”
The comment sparked fury among some Remain campaigners who objected to being linked to jihadis.
Virendra Sharma, the Labour MP for Ealing Southall, accused Bannerman of “putting a knife into free speech”.
But it was pointed out that Remainers have themselves likened Brexiteers to jihadis, notably in a speech by Lib Dem leader Vince Cable which was reported to the police as a hate crime.
Others such as Tory MP Anna Soubry regularly liken Leave supporters to “extremists”.
Mr Campbell Bannerman told the Daily Express that he had “no regrets” about the Tweet.
He said: “Remainers seem to be getting a bit sensitive.”
His Tweet follows concerns at the way that Remain supporters have appear to side with Brussels in the Brexit negotiations and whipped up fake Project Fear stories warning of an economic collapse.