Greens eye off Batman by-election

The Greens are ready to swoop on the marginal Labor seat of Batman as the dual citizenship fiasco threatens to bring down sitting federal MP David Feeney.

Mr Feeney will ask to be referred to the High Court on Thursday if documents relating to his UK citizenship renunciation can't be found in time, potentially triggering a by-election in his inner-Melbourne seat.

Greens leader Richard Di Natale said the minor party would look to build on its shock victory in the state seat of Northcote, which it won from Labor in a by-election in November.

Both seats border the Melbourne electorate held by the Greens MP Adam Bandt.

Senator Di Natale said any by-election in Batman would give the Greens a chance to continue their progressive push back against the major parties.

He was critical of Mr Feeney for taking so long to declare his potential citizenship issues.

"The fact that we have David Feeney, five months after this issue. broke, who is scrambling for his paper work - or so he says - means the man is either incompetent, or worse, he's lying," Senator Di Natale told reporters in Canberra on Wednesday.