Julian Assange threatened to sue The Guardian last year when he learned it planned to publish stories based on leaked US diplomatic cables without his permission, it's claimed today.

The Wikileaks founder's gripe: That the paper had obtained the documents it intended to use not via him, but from a leaker within his organisation.

In November, Assange stormed into the office of editor Alan Rusbridger with lawyer in tow, a new Vanity Fair article says. The Australian had previously had the newspaper sign an undertaking that no stories based on the cables would be published until he gave the go-ahead.

However, The Guardian has subsequently obtained a second copy of the 1.6GB cache of 250,000 documents (only a few hundred have been published to date) via Heather Brooke*, a freelance journalist with contacts inside Wikileaks. The newspaper believed this separate, "unofficial" source released it from any confidentiality covenants with Assange.

He disagreed. According to Vanity Fair he was "enraged that he had lost control... arguing that he owned the information and had a financial interest in how and when it was released".

Assange was eventually calmed by the promise of a short delay to allow him to brief French and Spanish newspapers that the release was imminent, plus "a great deal of coffee followed by a great deal of wine".

"Much to come on the Wikileaks story," Brooke wrote on Twitter this morning. "Vanity Fair article is just the tip."

Like Assange, and his former colleague Daniel Domscheit-Berg, who left Wikileaks last year criticising his leadership, Brooke is preparing a book covering the organisation's year in the spotlight.

Nevertheless, today's story casts new light on the breakdown of relations between Wikileaks and The Guardian , the newspaper associated most closely with its mega-releases of intelligence reports from Afghanistan and Iraq, and the US diplomatic cables. The antipathy was first exposed before Christmas, when Assange complained to other newspapers about how his erstwhile primary media partner had reported on a leaked document relating to the sex charges he faces in Sweden.

It has been widely noted that both disputes suggest Assange has a rather a weak grasp of irony.

Nick Davies, the journalist who obtained the Swedish file, and brokered the original deal between Wikileaks and The Guardian , fell out with Assange long before his legal threat, Vanity Fair also reports. The pair have not spoken since late July, it's claimed, after Assange told Davies he had given the Afghan files to Channel 4, which the latter believed broke their exclusivity agreement.

Davies has since accused Assange and his lawyers of issuing misleading statements over the sex allegations against him. The Wikileaker-in-chief is due in court next Tuesday for the preliminary hearing in Sweden's attempt to extradite him over the sex allegations made against him by two women. ®

*Though she said on Twitter this morning the article is "not exactly correct" regarding her role.