Labour MP Trevor Mallard has lodged an official complaint about Act leader John Banks failing to disclose a $15,000 donation was from SkyCity during his 2010 Auckland mayoralty campaign.
Mr Mallard lodged the complaint with the Auckland Council electoral officer this week. He also asked the electoral officer to scrutinise "anonymous" donations of radio advertising Mr Banks had included in his return.
SkyCity gave $15,000 each to Len Brown, now mayor, and Mr Banks, his rival, during that campaign.
Although Mr Brown's donation return listed SkyCity as a donor, Mr Banks' listed an anonymous donation of $15,000. It did not mention SkyCity.
The penalty for knowingly filing a false return is up to two years in prison or a fine of up to $10,000.