Prime Minister Julia Gillard has been accused of possibly prejudicing any future case against WikiLeaks founder Julian Assange by claiming he is "guilty of illegality" for leaking US diplomatic cables.

Mr Assange is expected to meet with British police sometime in the next 24 hours after Swedish authorities issued a fresh warrant for his arrest over alleged sexual offences.

Mr Assange and his lawyers say they will fight any extradition from the UK because they fear he will be handed over to authorities in the US, where he has been dubbed a "high-tech terrorist" and an "enemy combatant".

This morning Ms Gillard said: "Let's not try and put any glosses on this. It would not happen, information would not be on WikiLeaks if there had not been an illegal act undertaken."

"The Australian Federal Police is going to provide the Government with some advice about potential criminal conduct of the individual involved," she added.

"People would be aware that there's also the issue of a warrant relating to an alleged sexual assault in Sweden. What I would say about the publication of the WikiLeaks information is it's grossly irresponsible.

"We've got the Australian Federal Police looking to see whether Australian laws have been broken, and then we've got the commonsense test about the gross irresponsibility of this conduct."

But some Australian legal experts question whether Mr Assange has broken any law.

Liberty Victoria president Spencer Zifcak says he is shocked by Ms Gillard's statements.

"I was astonished actually," he said.

"As a lawyer, and presumably a highly competent one, that in this context she would have made a statement that was so highly inappropriate.

"One can imagine the reaction of a jury on hearing the person whose trial they're involved in has been said by the Prime Minister to be guilty. I'm really very surprised by it.

"There is no charge, there is no trial, there is no properly constituted court, and yet the Prime Minister deems it appropriate to say that Mr Assange has committed a criminal offence.

"That is a statement without foundation, it pre-empts the outcome of any proceedings, it denies him the presumption of innocence and it prejudices his right to fair trial."

Lawyers for Mr Assange say Ms Gillard may have behaved illegally by defaming their client.

One member of his legal team, Jennifer Robinson, says the Prime Minister's assertion that the website's publication of the documents is illegal goes too far.

"Her comments were made outside of Parliament so they're certainly not privileged, and I think it was misguided to suggest that he had committed a crime in England and, indeed, defamatory," she said.

"Although I think that Prime Minister Gillard's account will probably come at the ballot box."

Professor Zifcak says WikiLeaks does not seem to have done anything illegal.

"All WikiLeaks has done is publish documents that have been given to it. Now the interesting thing about that is WikiLeaks is publishing these documents in association with some of the great newspapers of the world.

"So if WikiLeaks is to be charged with the disclosure of official information then presumably these major newspapers will also be in the guns.

"But I can't see the authorities, either in Australia or the United States, pursuing those newspapers."

Professor Zifcak says he has written to the Prime Minister to express his concern about her comments.

The latest publications by WikiLeaks have prompted more accusations of crime.

US secretary of state Hillary Clinton says the release of a secret list of critical infrastructure is deeply distressing and the illegal publication of classified information poses real concerns and dangers.

But the director of the Centre for International Law at the University of Sydney, Dr Ben Saul, says Mr Assange is the victim of an international smear campaign.

"Julian Assange has become a target of a kind of global campaign to demonise him as a criminal, as a terrorist," he said.

"I mean, this is pretty serious stuff. And the Australian Government hasn't said very much on the public record to suggest that they're looking out for his interests in any kind of serious way."

Dr Saul says the most likely avenue for prosecuting WikiLeaks is through the development of international laws which protect diplomatic correspondence, but even that would be problematic.

"We know that some of the disclosures by WikiLeaks have genuinely been in the public interest: that is, disclosure has involved US war crimes, for example, in Afghanistan and Iraq.

"The disclosure that the US secretary of state, Hillary Clinton, ordered a campaign of espionage against the United Nations secretary-general, I mean, these are properly matters in the public interest.

"So if the law on diplomatic inviolability is to be extended globally to all kinds of diplomatic information then there really needs to be a kind of exception or carve out for the disclosure of illegal conduct.

"It doesn't make sense to absolutely protect the inviolability of diplomatic information if that just becomes a shield for government lawlessness."