Signatories to a letter delivered to Theresa May on Tuesday also include more than 50 members of the House of Lords, including four former chiefs of defence staff.
They are calling on the government to “put in place a lasting legal protection” for servicemen “wherever and whenever they serve”.
Referring to a controversial inquiry into British troops’ actions in Iraq, which has now closed after becoming widely discredited, the group warned veterans who served during The Troubles in Northern Ireland could be subject to a similar scenario.
The letter, organised by former minister and ex-territorial army officer Mark Francois, states: “The Iraq Historic Allegations Team furore showed us how our judicial system can be abused and how it can damage our security services.
“The legacy of the Northern Ireland Troubles threatens to do just the same, and we believe it is time for the government to act comprehensively and put it all behind us.”
The issue has previously been the source of a cabinet divide.
Earlier this year, Defence Secretary Gavin Williamson warned Northern Ireland Secretary Karen Bradley of a “witch-hunt” over government plans to consult on the setting up of an historical investigations unit in Northern Ireland, which is required as part of the 2014 Stormont House Agreement.
The prime minister has described an “unfair situation” at the moment in Northern Ireland, with terrorists “not being investigated” unlike former UK servicemen.
In the letter, signed by a total of 106 Conservative MPs, the prime minister is warned the current process of investigating and reinvestigating veterans – as well as the Stormont House Agreement proposals – are “completely at odds” with government manifesto commitments in the Armed Forces Covenant.
Mrs May is urged to take “clear and early action” to “remedy this situation”.
Some of the letter’s signatories, including former defence secretary Sir Michael Fallon, helped deliver their demands to 10 Downing Street in person on Tuesday.
Lord Dannatt, former head of the army and a platoon commander in Northern Ireland in 1971, said: “The present system of historic and current investigations is demonstrably not balanced, fair, equitable and, crucially, is not proportionate.
“The British army is a national institution which should be regulated under the authority of the Westminster parliament, not allowed to become victim to the intrigues of Stormont.
“The welfare and duty of care towards servicemen and military veterans should be clearly championed by the secretary of state for defence and not left to the outcome of a consultation by the Northern Ireland secretary.
“The British government must stand up for its security forces and must not be allow itself to be sleep-walked in line with the Republican agenda.”
Tory backbencher Johnny Mercer, who served in three tours of Afghanistan, said: “The pressure will keep increasing on this issue.
“It is one that a modern Conservative Party can unite around – the pursuit of elderly vets must end.”