© Eduardo Munoz / Reuters
The PM said that while allegations should be properly investigated, a culture of abusing the system had to be avoided.
"We can be proud also of the disciplined way in which our armed forces operate. But what is important is, if there are allegations - proper allegations - of criminal activity, those need to be investigated," she told the BBC.
"But what we do need to make sure is that there isn't an industry of vexatious allegations coming forward. I think measures have been taken."
On Monday a serving major who may face charges in connection with the drowning death of Iraqi teen Ahmed Jabbar Kareem Ali in British Army custody in Basra in 2003 pledged to hand himself into a war crimes court because he didn't trust he would receive a fair trial in Britain.
The decorated officer is currently on sick leave suffering with post-traumatic stress disorder, but hopes that his gesture will see the International Criminal Court (ICC) "finally and definitively put to rest this 13-year witch-hunt that seemingly has no end."
His comments come a day after former army captain turned Tory MP Johnny Mercer claimed that he had challenged then PM David Cameron on the issue of troops being threatened with prosecution in March.
He says he was told that Attorney-General Jeremy Wright - Britain's top lawyer - had overruled attempts to stop the Iraq Historic Allegations Team (IHAT) pursuing investigations.
In his scathing letter, which was seen by the Daily Mail, the major told Defence Secretary Michael Fallon: "You mentioned the ICC and how IHAT was a useful way of avoiding that eventuality."
He said that to make things easier he was "willing to travel to the Netherlands and hand myself in, as there is probably more chance of a fair and timely trial there, because in the UK there is no judicial process."
Comment: Yes, soldiers must be held accountable for war abuse but this only distracts from the real war mongers who need to be put on trial and convicted: