Mr Wilkie, who took the seat of Denison from Labor, said his support of a returned Gillard government would only extend to not voting for "unwarranted no confidence" motions.

He would also pass supply motions.

He said he remained concerned at many parts of Labor's policy agenda, including their treatment of refugees, but he would use the parliamentary term to champion appropriate reforms.

Mr Wilkie said he believed Labor held the best chance of forming a stable government for the next three years.

"I have decided to support the ALP. A future Gillard Labor government would have my vote," he told reporters.

"I will approach every policy on its merits."

Mr Wilkie's support gives Labor, who yesterday signed a formal agreement with the Greens, effectively 74 seats - meaning they need the backing of two of the three rural independent MPs to reach a 76-seat majority in the House of Representatives.

The trio, Bob Katter, Rob Oakeshott and Tony Windsor, are still receiving briefings from departmental officials.

Mr Wilkie said he hoped the trio would support his decision, and indicated the revelation last night by Treasury of a discrepancy of up to $10 billion on the Coalition's costings, might have been a persuasive influence on those talks.