Wellington, June 18 NZPA - Political parties are defending using taxpayer money to campaign in the Mt Albert by-election.

The New Zealand Herald reported today that many of the MPs who helped their colleagues in the Saturday by-election had scheduled other "parliamentary business" in Auckland at the same time, enabling them to claim for expenses such as accommodation.

The newspaper said 12 Labour MPs backed successful candidate David Shearer in the electorate, while National's Melissa Lee had three and the Greens' candidate and co-leader Russel Norman was supported by two colleagues.

MPs have unlimited domestic air travel but other expenses such as accommodation, taxis and rental cars are not covered if they are incurred while MPs are campaigning for their party.

MPs would not give details of their spending to the New Zealand Herald.

National whip Chris Tremain told the newspaper his party's MPs "acted in accordance with the rules", while Labour whip Darren Hughes said MPs had been reminded to pay their own costs if they were solely in Mt Albert for election purposes.

He said the "vast majority" visited while in Auckland on parliamentary business.

Greens co-leader Metiria Turei said Green MPs acted within the rules and the party would release total spending annually.

National list MP Aaron Gilmore, from Christchurch, said he was in Auckland for an education meeting, arranged weeks before, and only spent about two hours campaigning.

Dunedin South Labour MP Clare Curran said her campaigning coincided with meetings and work related to her communications and information technology portfolio.

Parliamentary Service general manager Geoff Thorn told the Herald MPs were "honourable people" and he did not think there were any problems.

The service relied on the MPs certifying that their expenses were incurred on parliamentary business and "the transaction cost of checking every individual trip simply doesn't make it worthwhile".

Otago University associate law professor Andrew Geddis said paying for campaigning trips from the public purse was state funding of political parties by stealth.

"This is not remarked upon when everyone jumps up and down saying political parties shouldn't get state funding for elections -- they already do."

Speaker Lockwood Smith is looking at rules around disclosing expenses.