Carr’s appointment comes in a Gillard cabinet re-shuffle, after she clung onto power during a failed leadership challenge from Rudd.

Gillard has appointed Carr – a respected former premier of the NSW government – via a vacancy in the senate created by the resignation of Mark Arbib – a Gillard loyalist – during the Rudd-Gillard fallout.

Carr’s assumption of the foreign affairs portfolio should have been a political masterstroke, but instead Gillard has been criticised as untrustworthy since she initially denied Carr would be drafted.

Carr was NSW’s longest-serving premier. He retired after 10 years in power, but said he “couldn’t have found it within myself to say no” when he was offered the chance to return to public service.

He said: “She asked me to serve my country, I couldn’t have said no to that.”

There has been much bloodletting over the appointment, with reports that ministers, including Stephen Smith, who holds the defence portfolio, tried to block Carr’s elevation.

The opposition leader, Tony Abbott, said the affair revealed how “faceless men” were able to dictate terms to the prime minister.

Echoing Kevin Rudd’s sentiments, he said it showed “you can’t believe anything she says.”

Rudd resigned as foreign minister to challenge Gillard for the Labor leadership and therefore the prime minster’s position. He lost by 31 votes to Gillard’s 71, and has promised to remain on the backbench and not challenge her again.

Robert McClelland, a Rudd loyalist, was demoted to the backbench as part of the reshuffle. Stephen Smith, who preceded Rudd in foreign affairs, will remain as defence minister.

In Australian politics, a party can appoint a replacement for a departing senator, without the need for a by-election.