The leader of the Green party has said people should not be banned from joining the Islamic State (Isis) or Al Qaeda.
Natalie Bennett said inciting violence or supporting violence should be illegal, but individuals should not be punished for being members of a terror organisation.
According to Green Party policy "it should not be a crime simply to belong to an organisation or have sympathy with its aims, though it should be a crime to aid and abet criminal acts or deliberately fund such acts."
Speaking on BBC1's Sunday Politics, Bennett was asked whether the policy meant, under the Green Party, it would be legal for people living in Britain to join terrorist groups such as IS.
"This is a part of our policy that I think dates back to the age of the ANC and apartheid South Africa" Bennett replied.
When asked how the policy applies specifically to IS in view of the terror threat to Britian, she replied: "What we want to do is make sure we are not punishing people for what they think or what they believe. Obviously actions of inciting violence, supporting violence, those are absolutely unacceptable, illegal and should be pursued to the full extent of the law.
"What we are talking about is a principle that you shouldn't be punished for what you think. And we need to balance, we do not protect freedom by destroying it."
Membership of IS was declared illegal last year when it became a proscribed organisation.
Defending the decision at the time, security minister James Brokenshire said: "'Proscription is a useful weapon in the armoury at the disposal of the government, police and security service to disrupt terrorist activity and protect the UK."
On Thursday, Foreign Secretary Philip Hammond warned that Britain is at "very significant risk" from a terror attack by radicalised Muslims, and warned against complacency in the fight to "disrupt these plots before they come to the stage of an attack."
"We have to regard Isil (IS) as probably the greatest single immediate threat to Britain's national security at the moment," he explained. "There's a very significant risk of an Isil-inspired attack being planned and, if we are not successful in intercepting it, executed by Isil sympathisers who live in the UK but are inspired by what is going on in Iraq and Syria."
So far, 600 people from Britain are believed to have travelled to Syria and Iraq to become jihadists.
Following the recent attacks in Paris the head of MI5, Andrew Parker, warned that Al-Qaeda is now planning a "a large-scale massacre" in the UK.