Julian Assange has hired lawyers to investigate suing the Prime Minister, Julia Gillard, for defamation over a claim that WikiLeaks acted ''illegally'' in leaking about 250,000 US diplomatic cables.
In an interview from the Ecuadorean embassy in London, Assange said Ms Gillard's comment, made in late 2010, was used by Mastercard Australia, which joined an online financial blockade of the organisation.
The White House and the Gillard government have condemned the release since November 2010 of more than 250,000 classified US diplomatic cables.
''I absolutely condemn the placement of this information on the WikiLeaks website. It's a grossly irresponsible thing to do, and an illegal thing to do,'' Ms Gillard said several days after WikiLeaks began releasing the cables.
The Australian activist group GetUp! recently interviewed Assange in his makeshift home inside the embassy, where he is staying as part of a bid to avoid extradition to Sweden, where he is wanted for questioning over sexual assault allegations.
He said he would be vulnerable to arrest in Sweden by the United States Justice Department, which is examining the possibility of charging people associated with WikiLeaks with espionage.
Mr Assange said the group's work was stymied by Ms Gillard's comments.
''Mastercard Australia, in justifying why it has made a blockade preventing any Australian Mastercard holder from donating to Wikileaks, used that statement by Julia Gillard as justification,'' Assange said.
''So the effects of the statement are ongoing and they directly affect the financial viability of WikiLeaks,'' Assange said. ''We are considering suing for defamation. So I have hired lawyers in Sydney and they are investigating the different ways in which we can sue Gillard over that statement.''
Assange said the comments were particularly damaging because they ''licensed'' other forms of attack on him and Wikileaks.
During the interview, Assange also revealed the effects of the past two years on his family, saying his young children have had to move homes and change their names.
GetUp!'s national director, Sam McLean, said the interview was the first step in a campaign calling on the Australian government to seek a commitment from the US that it will not try to extradite Assange over his publishing work with WikiLeaks.
''For too long the Prime Minister and the foreign ministers have put the interests of the US government ahead of Australian citizens. That is not good enough,'' Mr McLean said.
''Our government must demand a binding agreement from the US that they will not seek the extradition of this Australian citizen for his work as a journalist and publisher.
''GetUp! members expect the government to stand up for all Australians, even when it is not politically convenient.''