Violent extremists and so-called preachers of hate are to be banned from entering Britain under measures set out by home secretary Jacqui Smith.
Smith on Tuesday unveiled plans to strengthen rules excluding people "suspected of stirring up tensions".
As well as extremist clerics, the rules will apply to anti-abortionists, animal rights extremists and neo-Nazis.
Under the plans, some extremists will be named, with lists of the barred individuals published and shared with other countries.
Currently, it is up to the Home Office to prove that an individual holds extremist views. But the new rules see the burden of proof passed to those concerned, who will be required to publicly denounce or retract their alleged views.
The government will also make greater use of UK "watch lists" to ensure that previous extremist activities are accounted for when individuals seek to come to the UK.
"Through these tough new measures I will stop those who want to spread extremism, hatred and violent messages in our communities from coming to our country," Smith said.
"Coming to the UK is a privilege and I refuse to extend that privilege to individuals who abuse our standards and values to undermine our way of life."
However, Liberal Democrats home affairs spokesman Chris Huhne described the measures as "eye-catching gimmicks" that "don't make us any safer at all".
"It doesn't deal with the people who are already here or indeed the people who are preaching hate over the internet," he said.
Some 230 people have been prevented from entering Britain since 2005, including 79 "preachers of hate", but their identities have only become public after they complained about the decision.
