Bill English appears to have inadvertently broken rules by having his taxpayer-funded self-drive car at his Wellington home rather than his official "primary place of residence" in Southland.

This breach was highlighted in Parliament yesterday by Labour, which accused Prime Minister John Key of breaking the law by allowing the Deputy Prime Minister to have the car in Wellington.

The response from senior Government Minister Gerry Brownlee was that the apparent breach had "bugger-all relevance" to running the country.

Mr Key made a change to the rules for ministers' perks that removed the requirement that their self-drive cars be based at their primary place of residence.

This change took effect on May 26, allowing Mr English to have his car with his family in the Wellington suburb of Karori, rather than at Dipton in his Clutha-Southland electorate.

It was confirmed yesterday that Mr English had his car in Wellington before May 26. Labour MP Pete Hodgson told Parliament this broke the provisions of the Civil List Act 1979.

The act sets down that the Prime Minister, as the minister responsible for Ministerial Services, must set the rules about ministers' perks, known as a "determination".

Mr Hodgson questioned Mr Key on this, asking him "to explain his role in allowing, until May 26, the law to be broken".

Mr Brownlee, standing in for the Prime Minister who had left the chamber, said: "There are big issues to be dealt with in this country, and the location of ministers' cars, and the garages where they keep their cars, is not something that has occupied a lot of the [Prime] Minister's time".

Mr English's assertion that Dipton was his primary place of residence has been controversial this year, because it allowed him to claim rent to live in the Karori property.

Mr Key yesterday said changing the rule about self-drive car was his idea, because it removed an impractical situation in which up to 11 ministers were using chauffeur-driven vehicles in Wellington because they did not have their self-drive cars.

Mr English said he was not aware he had broken the rules.

The Herald yesterday contacted six of the ministers who might have been affected to see if they too had inadvertently breached the rules, but received no response by deadline.