The system of addressing the legacy of past in Northern Ireland is "unbalanced", Theresa May has said.
The prime minister made the comment in a letter sent to army veterans.
They are campaigning to halt investigations and prosecutions of soldiers involved in killings during Northern Ireland's Troubles.
In the letter, Mrs May writes that she "would like to acknowledge the depth of feeling among many veterans about how past events are being investigated".
She added that her government has concerns that the system for dealing with Northern Ireland's past is "not working well in anyone's interests".
"That is why we agreed with the Northern Ireland political parties in the Stormont House Agreement in 2014, to establish new institutions that would investigate the past in a way that is fair and proportionate," Mrs May said.
Mrs May's comments echo sentiments previously expressed by Northern Ireland Secretary James Brokenshire.
He said that investigations into killings that occurred during the Troubles "disproportionately" focus on members of the police and Army.
That claim has been emphatically denied by the Public Prosecution Service and the Police Service of Northern Ireland (PSNI).
Figures obtained by the BBC last month also challenge the claims that investigations into Troubles killings have an undue focus on the security services.
Inquiries into killings by the Army account for about 30% of the PSNI's legacy workload.