A former cabinet minister says he's baffled by Michael Wood's repeated failure to declare shares.

Wood is resigning as a minister over failing to disclose shareholdings in the telecommunications and banking sectors.

It follows his previous failure to disclose or dispose of shares in Auckland Airport, despite repeated requests.

Peter Dunne - who resigned as a minister himself in 2013 after withholding information from an inquiry into a leak of a GCSB report - told Mike Hosking the Wood situation is truly bizarre.

He says after the warnings Wood received over his airport shares, he should at least have gone back to check if he was in the clear.

Chris Hipkins is now considering additional restrictions on ministers holding shares.

LISTEN ABOVE