Taking action: Legal weapons remain unused over decades

The issue is a politically delicate one because by the time any immigrant is applying for citizenship, he or she would be required to have lived in the UK for at least five years and already been granted residency rights.

Which effectively means that 104 people now identified as potentially taking part in human rights atrocities have had a comfortable existence in the UK for over five years – so comfortable they were intending to become full British citizens.

Clearly, not all those identified as suspects can automatically be classed as guilty but denying citizenship is a significant declaration of concern by the Home Office.

How those 104 people came to be granted an indefinite right to remain in the UK in the first place puts a major question mark against the original screening process.

The Home Office did set up a specialist war crimes team in the UK Border Agency in 2004 and it is likely that some of the cases pre-date it starting work. The lack of action on those discovered since then is more difficult to explain.

The right to deny war criminals refugee status was enshrined in a 1951 Geneva Convention, which was primarily concerned with offering sanctuary to refugees fleeing persecution.

And the Home Office admits that the Home Secretary has had powers to potentially remove suspected war criminals who have slipped through the screening process under immigration acts passed in 1971, 1999 and 2002.

Yet a spokesman confirmed it was only now that a "full policy to revoke indefinite leave to remain utilising the powers outlined is currently in active development".

He added: "This policy will, in due course, fully outline the level of evidence required to revoke indefinite leave to remain in a range of case types."

The Home Office provided the rider that a higher level of proof would be required for revocation and deportation than that required to deny citizenship.

No timescale was provided on when the new policy would be drawn up or implemented.

Consequently, those suspected war criminals who have already lived here for more than five years are likely to remain with impunity for several more.