The Home Secretary announced details of plans for the Government to block fanatics who join Islamist fighters in the Middle East from returning to Britain.
A new Counter-terrorism and Security Bill, introduced into Parliament yesterday, will also put new legal obligations on authorities in schools, councils and prisons to counter extremist ideas.
Mrs May told MPs: "This Bill includes a considered, targeted set of proposals that will help to keep us safe at a time of very significant danger by ensuring we have the powers we need to defend ourselves."
It's dangerous to rush through this grab-bag of measures without proper scrutiny or challenge
Amnesty International UK legal adviser Rachel Logan
Civil liberties campaigners raised concerns about some of the measures.
Shami Chakrabarti, director of rights campaign group Liberty, said: "This Bill is worse than we feared.
"Yesterday we learned that the authorities failed to follow suspects with the power and intelligence they already had - today they want more power to make us all suspects. When will they learn?"
Amnesty International UK legal adviser Rachel Logan said: "It's dangerous to rush through this grab-bag of measures without proper scrutiny or challenge.
"While the Government needs to ensure that anyone suspected of criminal activity is investigated, measures like invalidating passports and excluding British nationals from their home country push the boundaries of international law.
"Meanwhile, adding the internal exile of forced relocation to the already unfair Tpims regime is another measure which causes significant concern for basic freedoms. We simply don't have the fair and proper processes in place for such drastic decisions."
Plans to block suspected jihadists from returning to Britain in the Bill were "nothing like as dramatic" as David Cameron indicated they would be earlier this year, according to the Independent Reviewer of Terrorism Legislation, David Anderson.
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Mr Anderson described the original proposals unveiled by the Prime Minister in September to counter the threat from British extremists travelling abroad to fight for Islamic State (IS) as an "announcement waiting for a policy".
He told MPs and peers he believed that it had soon become clear that such a move would "neither legally nor practically" work and the plan was now for a system of "managed return".
The new counter-terror legislation will ban insurance companies from footing the bill for terrorist ransoms and powers will be re-introduced to relocate terror suspects across the country.
A statutory duty will be placed on named organisations - such as colleges, universities, the police and probation providers - to help deter radicalisation and, where organisations fail, ministers will be able to issue court-enforced directions to them.
Police are to be handed powers in the new Bill to force internet firms to hand over details that could help identify suspected terrorists and paedophiles, while police and border staff will be given the power to seize the passports of terror suspects.
Its second reading in Parliament - the first opportunity for MPs to debate the main principles of the Bill - will be announced soon.
Shadow home secretary Yvette Cooper said: "We have seen unprecedented numbers of people travelling from our country to join Isil (Islamic State of Iraq and the Levant) in Syria and Iraq, so more does need to be done to make sure there are rapid ways to remove someone's passport if they are about to travel to join the fighting, and also to deal with the threat from those who want to return.
"We will look at the detail of these proposals being put forward to prevent this to make sure they are effective and proportionate, with appropriate safeguards in place.
Read more:
http://www.express.co.uk/news/uk/540503/Theresa-May-terrorist-crackdown
