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Senior diplomats have accused the government of “putting lives at risk” over shadowy briefings accusing opposition MPs of “colluding with foreign powers” for criticising Boris Johnson’s Brexit strategy.

Two senior figures representing Britain abroad have told the Mirror they will launch complaints this week over briefings from inside No 10 which suggested the government might attempt to seize MPs email and phone records.

Yesterday Tory MPs announced they would introduce a new law that would see any British citizen who undermines Government negotiations abroad face jail in the wake of Boris Johnson's humiliation.

It comes after a senior No 10 source said told the Mail on Sunday that the government was working on "extensive investigations into Dominic Grieve, Oliver Letwin and Hilary Benn and their involvement with foreign powers and the funding of their activities".

They added that the government "will demand the disclosure of all details of their personal communications with other states".

But the accusation - which all three MPs strenuously deny - sent shockwaves through Britain's diplomatic networks.

(Image: WILL OLIVER/EPA-EFE/REX)

One official told the Mirror: “This is a witchhunt and it risks undermining the work we do abroad telling foreign governments not to prosecute, jail and harass opposition politicians who disagree with them.

"It cuts against more than 50 years of British foreign policy and it will put lives at risk.”

A second official confirmed that staff in the Foreign and Commonwealth Office were incandescent over anonymous briefings from No 10.

“Threatening MPs with investigation is something you would expect the government to be stopping abroad, not encouraging at home, ” they said.

(Image: Adam Gerrard / Daily Mirror)

Opposition politicians warned the government that it was playing with fire.

Labour's Shadow Foreign Secretary branded No 10s comments "outrageous" and warned that Downing St was "spiralling out of control".

Ms Thornberry told the Mirror: "Boris Johnson may not have been elected by the British people, but that does not give him the right to act like some despotic dictator, using public resources to investigate his political opponents."

The Liberal Democrats Foreign affairs spokesman Chuka Umunna said Downing St's behavior was designed to "suppress dissent".

He said: “This would take us down a very dangerous avenue indeed and has a whiff of the 1930s about it - the threat of the harassment and persecution of opposition politicians, and an attempt to suppress dissent, by a right wing, nationalist government.

"We must fight this tooth and nail for the sake of our democracy.”

Senior figures within the diplomatic service are expected to raise behind the scenes complaints with No10 this week - with formal complaints threatened if the rhetoric doesn't die down.