Labour leader Andrew Little says Judith Collins' sponsorship deal with an Auckland car dealership cheapens her as an MP.
"I think it's completely out of order," Mr Little told reporters this morning.
A South Auckland dealership has given the former Justice Minister and National MP a car to use for six months and is covering her petrol costs. The deal is within the rules for an MP as long as Ms Collins declares it as a pecuniary interest.
Mr Little said her promotion of the dealership "cheapens the role of being an MP and it cheapens Judith Collins".
"No MP should be selling themselves as some sort of sponsorship product," he said.
The Labour leader said it did not matter that the car promotion was within the rules.
"The idea that an MP would become a sponsored product, even if there's a charitable purpose to it, is a total detraction from the public responsibilities that an MP has."
Green Party co-leader James Shaw has also criticised the sponsorship deal.
Ms Collins defended her ambassador role for the company by saying that she was saving the taxpayer money and was using it to raise money for Papakura Crimewatch.
Prime Minister John Key said this morning he had no problem with Ms Collins' sponsorship deal as long as she followed the rules for MPs, such as disclosure of a pecuniary interest.
Mr Key said that if Ms Collins returned to Cabinet she would have to reconsider her role with the company.
"She would have to adjust her behaviours to be in line with the Cabinet manual."