Cabinet minister Judith Collins spent more than $100 a week on petrol over 13 months for her ministerial self-drive car, even though she has a chauffeur-driven Crown limo at her disposal.

Documents obtained by 3 News showed that from February 2009 to February this year, Ms Collins' petrol bill was $5721.14, or about $440 a month.

Whanau Ora Minister Tariana Turia spent $268 a month, followed by Agriculture Minister David Carter, with $218 a month.

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