PNG's high commissioner Charles Lepani has written to new Foreign Minister Bob Carr in protest over his comments.

Long-time friend of the US: Foreign Minister Bob Carr. Photo: Penny Bradfield

Bob Carr may have been Foreign Affairs Minister for only 12 months, but he started talking to United States diplomats about internal Labor politics nearly 40 years ago.

Previously secret US embassy and consulate reports incorporated into a new searchable database unveiled by WikiLeaks on Monday reveal that Mr Carr was a source for US diplomats seeking information on the Whitlam government and the broader Labor movement in the mid-1970s.

Then a rising star in NSW Labor, Mr Carr was quick to join in criticism of prime minister Gough Whitlam as the federal Labor Government encountered growing political and economic difficulties after the May 1974 federal election.

In August 1974, the US Embassy in Canberra reported at length on what it described as "a pervasive sense of gloom and anxiety" as the Whitlam government “struggle[d] in [a] disorganised fashion to stem growing inflation”.

Together with NSW Labor president John Ducker, Mr Carr candidly told the US consul-general in Sydney that "economic policy has never been Whitlam's bag" and criticised the prime minister's "tendency to delegate practically everything".

A former Australian Young Labor president and then education officer with the NSW Labor Council, Mr Carr later "expressed deep concern to [the US] consul general over [the] impact of Labor disputes on the prospects of [the] Labor Government".

Asked about his 1970s contacts with US diplomats, Senator Carr said on Monday: "I was in my 20s. I could have said anything."

The once-confidential cables also suggest that US diplomats turned to Mr Carr as a source of background information on Labor political figures: for example Mr Carr explained that a speaker at a pro-Palestinian demonstration in 1975 – left-wing Labor parliamentarian George Petersen – was "a NSW equivalent of Victoria's [Bill] Hartley".

Senator Carr has long been a very strong supporter of Australia's alliance with the United States and has a keen interest in US politics and history.

In his early conversations with US officials, he appears to have followed the lead of Mr Ducker, his NSW Labor right faction mentor, who advised the US on industrial relations issues and internal Labor politics, and dismissed critics of the US alliance as being engaged in "emotional, silly expression lacking in substance and characteristic of the silly left-wing fringe of the ALP".

US embassy cables leaked to WikiLeaks in 2010 revealed that another senior NSW Labor right faction leader, former Senator Mark Arbib, was a more recent "protected" US embassy source providing inside information and commentary on Labor politics.

About 11,000 cables from the US embassy in Canberra and consulates in Sydney and Melbourne between 1973 and 1976 are part of a massive trove of more than 1.7 million electronic documents that were transferred to the US National Archives and Records Administration in 2006.

However the records have been largely neglected by historians, owing to the absence of an effective search engine.

WikiLeaks has incorporated a copy of the entire electronic archive into an easily searchable database that also includes the more than 250,000 US diplomatic cables leaked by United States Army private Bradley Manning.

With more than two million documents and more than a billion words, WikiLeaks's Public Library of US diplomacy is the largest electronically searchable diplomatic archive available to historians, journalists and other researchers.