Fifty-seven medals returned by veterans are being kept by the Ministry of Defence (MoD) as the government continues to face a backlash over moves to prosecute soldiers accused of crimes during the Troubles.

Downing Street has written to former soldiers who returned their Northern Ireland service medals to say they will be kept in case of a change of heart but that a decision may have to be taken to dispose of unclaimed medals in the future.

The number of medals being stored after veterans returned them was revealed following a freedom of information request to the Ministry of Defence, which has recently announced proposals to grant immunity for offences committed more than 10 years ago in Iraq, Afghanistan or anywhere else outside the UK.

Returned medals have included those that formed part of a protest in March, which involved 22 members of the cabinet who had not served in the armed forces being sent military decorations packaged with white feathers, traditional symbols of cowardice.

Jim Kenyon, a former mayor of Hereford and a Parachute regiment veteran, said that the 22 had “stood by” and allowed a former Parachute regiment lance corporal, identified only so far as “Soldier F”, to stand trial for murder and attempted murder for his role in the 1972 Bloody Sunday killings.

He told the Guardian that he and other veterans who had sent the ministers their medals and decorations had yet to receive any response from the MPs.

“They were packaged individually and sent to each MP with the name of a soldier who had been killed, but we’ve heard nothing,” Kenyon added.

“I might consider writing again and asking for it back if things changed, but for me it was a price worth paying. In Northern Ireland I had an RPG fired at me when I was on sentry duty and that’s only one experience. Now they want to drag old men through the courts.”

However, some veterans who have returned medals have been receiving letters from the head of direct communications at the Cabinet Office, which state: “I can assure you that it has never been the government’s intention to cause concern to past and present personnel that leads them to feel the need to surrender their treasured awards. We will always be indebted to those who have served their country.

“In situations such as these, any returned medals will be held in safe-keeping by the Ministry of Defence medal office in case the individual has a change of heart and wishes for them to be returned. That said, a decision may have to be taken to dispose of unclaimed medals in the future.”

Medals have been returned in the past for other reasons, including as protests against British military actions in Afghanistan, Syria and Iraq.

Penny Mordaunt, the defence secretary, said earlier this month that she wanted soldiers who served during the Troubles to be covered by proposals to introduce an effective amnesty from prosecutions for all other military veterans.

The minister said she wanted to implement “a wider solution for the veterans’ community”, despite the fact the Northern Ireland secretary, Karen Bradley, has repeatedly ruled out amnesties.

The Guardian revealed in April that as many as 200 former members of the British security forces are under official investigation for alleged criminal actions during the Troubles as a rift opens up between the Northern Ireland Office and the Ministry of Defence over how to deal with historical accusations.