The British government is proposing to strengthen the law on genocide after warnings that Britain could become a "safe haven" for war criminals.
Under the plans, British residents suspected of committing or conspiring to commit genocide since 1991 could be tried in a domestic court.
Currently the law applies only to crimes committed since 2001.
If enacted, it would mean that suspects in the Rwandan and Yugoslavian atrocities of the early 1990's could be bought to justice in Britain.
Justice Secretary Jack Straw said amendments would be made to the Coroners and Justice Bill in the House of Lords in the autumn.
But he warned making the changes would be "quite complex".
An anti-genocide group, the Aegis Trust, believes there are as many as 18 suspected war criminals living in Britain from countries including Afghanistan, Sudan, Sierra Leone and Sri Lanka.