London: At least 50 suspected Islamist terrorists have been stripped of their passports in a crackdown ordered by the UK government.

UK Home Secretary Theresa May has told The Sunday Times that "since 2013, 30 people have had their passports permanently removed" using royal prerogative powers that allow enemies of the state to be stripped of citizenship and "around 20 have had their passports temporarily seized" under rules introduced earlier this year to stop people travelling to Syria to join ISIS.

Ahead of the Conservative party conference in Manchester, May, 59, said that the British government's extremism strategy, laying out the next steps to tackle the spread of militant Islamism, will be published this month.

"Universities have a duty of care to their students but if someone has been radicalised on campus to the extent that they would go out and harm themselves and others, I think universities ought to be concerned. It is a requirement on them to prevent people being drawn into terrorism," she said.

The new strategy will contain tougher rules for broadcasters on hate preachers getting air time and it will help to beef up a police unit that has removed 4,000 pieces of extremist material from the internet each month.

"We will be looking at legislation to disrupt extremist activity but I've excluded more hate preachers than any previous home secretary from coming into the country at all," she added.

She has banned 97 hate preachers from entering Britain since she became home secretary in 2010, as well as presiding over the removal of the high-profile extremist figures Abu Qatada and Abu Hamza. In the three years prior to that, the Labour government excluded 56 hate preachers.

May is the longest-serving home secretary of Britain in half a century and is seen as a serious contender for the Tory party leadership.

The migrant crisis has prompted May to tell her EU counterparts to ditch the principle of freedom of movement. Many in her party regard this as unrealistic but she is adamant David Cameron can make progress in ending some of its worst abuses as part of the EU renegotiation.

"There has been a growing interest in Europe in terms of looking at things like sham marriages. I'm confident the prime minister will be able to negotiate a good package," she said.