Labor's Feeney resigns from parliament

Labor faces the loss of one of its federal seats to the Greens after MP David Feeney quit politics over the citizenship fiasco.

The government says Labor leader Bill Shorten has been humiliated by the party's first citizenship casualty and faces a test in what will be a tough by-election in Mr Feeney's marginal Melbourne seat of Batman.

The High Court had asked Mr Feeney to produce documents by Thursday showing he had renounced his British and Irish citizenship.

However Mr Feeney has been unable to locate sufficient evidence proving his British citizenship renunciation - which he thought had been registered 10 years ago.

"On this basis having regard for my duty under section 44 of the constitution I have today written to the Speaker of the House of Representatives resigning as an MP effective immediately," he told reporters in Melbourne.

Evidence concerning his Irish renunciation was "intact", Mr Feeney said.

Mr Shorten, who had insisted his team was clear of any citizenship issues, said he was shocked when Mr Feeney initially came to him saying he may have issues.

"I asked him to find material that corroborated his explanation - as he has explained today, he has been unable to do so," Mr Shorten said.

"This decision is the right one and spares the valuable time and resources of the High Court."

Prime Minister Malcolm Turnbull told reporters in Toowoomba the resignation was "long overdue".

Liberal frontbencher Christopher Pyne said it was a "day of humiliation" for Mr Shorten and the Labor leader should also seek the resignation of another MP, Queenslander Susan Lamb, over her dual citizenship.

By-elections could then be held in the seats of Longman and Batman on the same day, saving taxpayers' money.

Mr Feeney's margin in Batman was cut to one per cent at the 2016 election as Greens candidate Alex Bhathal secured a higher primary vote than Labor.

The sitting member was saved by Liberal Party preferences.

While Ms Bathal has already been selected as the Greens candidate, Mr Pyne declined to say whether the Liberals would stand but hinted it was inclined not to.

He said the by-election was a "test for Bill Shorten".

The Greens only current member of the lower house, Melbourne MP Adam Bandt, tweeted "David Feeney has just resigned -- IT'S ON!"

Asked about Labor's chances, frontbencher Mark Dreyfus said: "Of course Labor can win this seat. It's been a Labor seat for a very long time."

One of the possible replacements being flagged for Mr Feeney is ACTU president Ged Kearney, who considered running for preselection in the seat in 2013.

A by-election could be held as early as March 10.

After his brief statement, Mr Feeney embraced his wife and son Ned as two protesters held up "Stop Adani" signs and asked him what Labor was going to do to stop the mine.