The leak of private emails from the UK's ambassador to Washington is an act of "treason", according to Conservative MP Tom Tugendhat.
The Foreign Affairs Select Committee chair said it was a "betrayal" of the country for Sir Kim Darroch's emails to the UK government to be leaked to a newspaper, and called for the police to step in.
"This is extremely serious. I think the police should get involved and I think we should have prosecutions," Mr Tugendhat told talkRADIO's Julia Hartley-Brewer.
"We have had a long tradition now, sadly, of politicians leaking secret government information as though it did no harm. It does do harm. It undermines the British people, it undermines their influence and it undermines our security."
He continued: "It is absolutely wrong and it must stop."
Among the leaked messages was one describing the Trump administration as "inept".
Another questioned whether the White House "will ever look competent".
"I think there is probably someone in the UK, whether a minister or a senior official, who has leaked these for petty political advantage, and that isn't good enough," Mr Tugendhat added.
"It is a form of betrayal and that is wrong. Betrayal is another word for treason. Betrayal of your country is treason."
The Foreign Office have launched an investigation into how the leak occurred.
However, US president Donald Trump has already hit out at the ambassador for his words, claiming he is not a "big fan" of Sir Kim.