Concerns are being raised around a Cabinet Minister's ability to leave Parliament and become a lobbyist.

A new report by the Helen Clark Foundation is calling for tougher rules around political lobbying and donations to improve trust and confidence in political decision-making.

Former Attorney-General Chris Finlayson says he believes there should be a stand-down period.

"The idea that you finish up in Parliament on Friday and start lobbying on Monday is unacceptable, and I think most people would acknowledge that."

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