According to shocking new figures more than 800 people suspected of links to atrocities overseas have been identified since 2005 trying to secure shelter or settlement in Britain.
Many of those hiding in the UK come from countries such as Afghanistan, Iraq, Libya, Rwanda, Serbia, Sri Lanka and Zimbabwe.
It has fuelled concerns that Britain is seen as a safe haven for those wanted for crimes against humanity.
Michael McCann, the chairman of a cross-party parliamentary group to prevent genocide, said the worrying figures revealed the need for greater government transparency on the issue.
"The organization in the Home Office that used to deal with this - the UKBA (UK Border Agency) - was a basket case," the Labour MP for East Kilbride, Strathaven and Lesmahagow said.
"It had failed on so many different levels I've lost count,” he said.
"I have deep concerns that the Home Office isn't being as forthright as it could be and I think we should be drilling down into these cases in order to give the public of our country that security."
SHI/BA