The new defence secretary, Penny Mordaunt, declared that army veterans should not be “pursued unfairly for events that took place decades ago” hinting that she favoured an amnesty for British soldiers from historical prosecutions.

The minister was hoping to defuse a protest from Conservative backbencher Johnny Mercer who had said on Wednesday night that he would refuse to support the government in the Commons until fresh legislation is brought forward.

But while Mordaunt said questions about historical prosecutions had “dragged on for far too long and it is time for action” the cabinet minister stopped short of spelling out what she intended to do to tackle the contentious issue.

“We will always hold our armed forces and the chain of command to account but I want to ensure our service personnel are not going to be victims of unfounded allegations, as we saw in the case of IHAT, or pursued unfairly for events that took place decades ago,” the minister said, referring to the collapsed Iraq Historic Allegations Team.

Her predecessor, Gavin Williamson, was planning to bring forward legislation with a 10-year limit for cases to be brought to trial in response to concerns raised after news that a former paratrooper would be prosecuted for the murder of two people killed on Bloody Sunday in Derry in 1972.

It was not immediately clear if Mordaunt intended to follow Williamson’s lead by introducing a bill in a future Queen’s speech. The previous proposal was to introduce a statutory presumption against prosecution if the alleged offence took place over 10 years ago.

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Any attempt to ban or make prosecutions of army veterans more difficult would risk inflaming nationalist sentiment in Northern Ireland, at a time when many episodes from the time of the Troubles remain unresolved.

Sinn Féin said on Thursday that “no one is above the law”. Linda Fallon, a Sinn Féin member of the Stormont assembly, added there should be “no immunity or impunity for British forces guilty of crime, collusion and murder in Ireland”.

Mercer, a former army officer, had written to Theresa May to say that the “historical prosecution of our servicemen and women is a matter that is personally offensive to me” and demanded action from the prime minister.

The MP for Plymouth Moor View said that he would refuse to support the government over non-Brexit-related legislation until an end was brought to what he described as the “abhorrent process” of “elderly veterans being dragged back to Northern Ireland”.

Gavin Robinson, a DUP MP, said his party had “consistently raised the matter” with the the government, while the party’s leader, Arlene Foster, and senior colleagues met May at Chequers for a wide-ranging “policy discussion”.

Around 3,500 people died during the Troubles, and the task of investigating any unresolved murder cases is largely handled by the Legacy Investigations Branch (LIB) of the Police Service of Northern Ireland.

Last month the Guardian revealed that between 150 and 200 army veterans and police officers are believed to be under investigation. Military cases account for around 30% of the LIB’s workload, but only form 10% of the overall deaths from that period.

Thirteen protesters were shot dead at a civil rights march in Derry in 1972, which became known as Bloody Sunday, and the original inquiry was widely seen as a whitewash. In response to decades of campaigning, Tony Blair agreed to a fresh public inquiry, which took 12 years and cost £200m.

It concluded that soldiers had lost their self-control and that none of the people who were shot was posing a threat of causing death or serious injury. A police investigation followed, leading to the decision to mount a prosecution for murder of a man known only as Solder F last month.

Mercer didn’t immediately respond to Mordaunt’s comments.