An anti-corruption summit in London has been assured New Zealand is committed to tackling corruption despite not yet signing up to new international agreements.

Around 40 nations gathered to put together some kind of agreement and six countries have signed.

Police Minister Judith Collins was at the summit but says New Zealand wants to know more.

"But we are certainly going down the track of far more transparency particularly around the beneficial ownership," Ms Collins said.

A joint investigation into New Zealand's link with the Panama Papers by TVNZ, RNZ and investigative journalist Nicky Hager has led to claims that NZ is a tax haven for foreigners trying to avoid paying taxes in their home country.

The Panama Papers expose secretive offshore companies used to hide wealth, evade taxes and commit fraud.

I think we're about a footnote really. - Police Minister Judith Collins

Ms Collins believes revelations in the papers have not harmed New Zealand's reputation.

“New Zealand is committed to co-operating with our partners to help prevent illegal money flow across multiple countries caused by high level corruption, and undertake effective enforcement action against those involved."

British Prime Minister David Cameron says corruption is the cancer at the heart of many of the world's problems and he has promised to force all offshore firms that own property in England and Wales to reveal their ultimate owners in a publicly available register.