A sponsor of the National Party and prominent lobbyist has taken aim at the party's president Larry Anthony, saying he should not remain on the executive while running and owning a lobbying firm.

Mr Anthony, a director and part-owner of SAS Consulting Group, which represents large energy companies, has maintained he has no conflict of interest in occupying his commercial and political roles.

Nationals party president and lobbyist Larry Anthony. Credit:Alex Ellinghausen

Lobbying rules prohibit registered lobbyists from sitting on party executives but Mr Anthony said he was "not directly a lobbyist" and did not need to be registered.

Michael Kauter, who runs his own lobbying company Strategic Political Counsel, said "if you're a lobbyist or own a lobbying firm, I don't think you should be involved in running a political party, pure and simple – it muddies the water".