It seems the silent auctioning of paintings may be masking who's supporting the Labour Party

The party's the latest to be probed by the Serious Fraud Office, for donations in 2017.

It's already looking into the New Zealand First Foundation and an investigation into the National Party is before the courts.

Victoria University political donations researcher Max Rashbrooke says the donations of the art work are being registered to the artist.

But he says what we really want to know is who's paid large amounts of money for artworks, which is then going into the Labour Party's coffers.