David Cameron said that a long-awaited British assessment of the Muslim Brotherhood will be published this year - but appeared to signal that it will not be proscribed as a terrorist group.
The Prime Minister told Egyptian president Abdel Fatah al-Sisi that "what we do in Britain is we judge people by whether they are inside the law or outside the law" after the pair held talks in Downing Street.
The review was completed last summer amid calls from allies such as Saudi Arabia for the UK to impose a ban but is believed to have found little evidence to back such a change.
Ministers have been accused of sitting on the report to avoid upsetting the Saudis and other partners.
Cairo has waged a sweeping crackdown on senior figures from the Islamist group since its leader Mohammed Morsi was ousted as president by the military in 2013 and replaced with Mr Sisi.
"If people are fomenting violence then they are breaking the law and the law should come down on them," Mr Cameron told reporters after the talks.
"In terms of our review of the Muslim Brotherhood, which we discussed today, that will be published later this year and I think you will see, as you are already seeing in Britain, a much more robust approach against extremism, against extremism of all kinds, and against those extremists who stop just short of endorsing violence .. but nonetheless those extremists whose world view encourages people to pursue a course of violence.
"That is very much our approach here in the UK."
The Muslim Brotherhood played a key role in Egypt's 2011 revolution. It is considered a terrorist organisation by several countries but has also taken part in democratic elections on a peaceful platform.