The proposed legislation to be outlined by Penny Mordaunt would include an end to repeated investigations on historical operations and a statutory presumption against prosecution of current or former personnel for alleged offences committed in the course of duty abroad more than 10 years ago.
It will stipulate that such prosecutions are not in the public interest unless there are “exceptional circumstances”, such as if compelling new evidence emerged.
However, any new measures would not apply to cases arising in Northern Ireland.
Just last week, former army officer and now Tory MP Johnny Mercer said he would 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”.
Ms Mordaunt said: “We all owe a huge debt of gratitude to our armed forces who put their lives on the line to protect our freedom and security.
“It is high time that we change the system and provide the right legal protections to make sure the decisions our service personnel take in the battlefield will not lead to repeated or unfair investigations down the line.”
Ms Mordaunt is also expected to reaffirm the position announced by the government three years ago that it would take advantage of a right to suspend aspects of the European Convention on Human Rights at times of war.
At the time, Theresa May said the move should end an “industry of vexatious claims” which has seen veterans of Iraq and Afghanistan pursued through the courts over alleged mistreatment of combatants and prisoners over a decade after the supposed events took place.