The prosecution of British soldiers for alleged past crimes in Northern Ireland, and more recent conflicts in Iraq and Afghanistan, has dogged the military and government for years.

The legislation proposes measures to "reduce uncertainty arising from historical allegations and create a better legal framework to deal with claims from future overseas conflicts", according to the defence ministry.

The House of Commons passed the Overseas Operations (Service Personnel and Veterans) Bill by 345 votes to 260. It now heads for debate in the House of Lords, the UK parliament's unelected upper chamber.

Defence Secretary Ben Wallace told the Commons that the bill would deliver on the Conservative government's 2019 election promise to protect service personnel and veterans from "vexatious claims and endless investigations".

Veterans minister Johnny Mercer, a former army officer who served in Afghanistan, insisted the legislation "does not decriminalise torture" but strikes "an appropriate balance between victims' rights and access to justice".

However John Healey, defence spokesman for the main opposition Labour party, said the bill was "dishonest and damaging" as it would not prevent "baseless" investigations and could risk British troops getting hauled before the International Criminal Court.

The legislation discourages the prosecution of current or former soldiers for alleged offences committed on overseas operations more than five years ago.

It raises the threshold prosecutors will use in deciding to pursue a case after five years to "exceptional", and requires them to weigh the public interest and get consent from the attorney general before prosecuting.

The bill will restrict the discretion of courts to extend time limits for bringing civil claims for personal injuries, deaths and human rights act violations to a maximum of six years.

However, the government said military operations will continue to be governed by other international humanitarian law, and denied the bill amounts to an "amnesty" for UK troops.

The UK military has been accused of covering up credible evidence of war crimes by soldiers against civilians in Afghanistan and Iraq, according to leaks last year from two government-ordered inquiries.

In June, an independent British investigator looking into the Iraqi allegations said that all but one of thousands of complaints -- which ranged from rape and torture to mock executions and other atrocities -- had been dropped.

That followed a 2017 UK tribunal ruling that ex-lawyer Phil Shiner, who investigated and chronicled hundreds of the accounts of such crimes, was guilty of misconduct and dishonesty.