The former army officer turned Tory MP Johnny Mercer has said he will no longer support the government unless the historical prosecutions of ex-servicemen and women ends.
In a letter to the Prime Minister, he said he found the repeated investigations into allegations – some dating back decades – "personally offensive".
He said he was not to prepared to vote for government legislation – except on Brexit – until the government took "clear and concrete steps" to end the "abhorrent process".
Mr Mercer has campaigned against the pursuit of legacy cases from the conflicts in Northern Ireland, Afghanistan and Iraq since he entered Parliament in 2015.
He has also recently accused the Conservative chief whip's office of contacting former service colleagues to try to dig up dirt on him.
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In his letter to the PM he wrote: "As you know, the historical prosecution of our servicemen and women is a matter that is personally offensive to me. Many are my friends; and I am from their tribe.
"These repeated investigations with no new evidence, the macabre spectacle of elderly veterans being dragged back to Northern Ireland to face those who seek to re-fight that conflict through other means, without any protection from the government who sent them almost 50 years ago, is too much.
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"I will not be voting for any of the government's legislative actions outside of Brexit until legislation is brought forward to protect veterans from being repeatedly prosecuted for historical allegations."
He went on: "It has not been an easy decision to make. But this incident with your chief whip has forced my hand.
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"It appears that my values and ethos may be slowly, but very firmly, separating from a party I joined in 2015."