NZ First leader Winston Peters has been interviewed by detectives investigating allegations Brendan Horan took money from his late mother's bank account.
It came as Tauranga police confirmed they had stepped up their inquiry into Horan.
Police began assessing the claims after the case was referred to them by the Serious Fraud Office in January. "This assessment is complete and has now moved to an investigation phase being led by Tauranga Criminal Investigation Branch," a spokeswoman said.
Peters refused to discuss his police interview, saying he didn't want to "waste his time" on Horan.
Horan, who was on holiday in the Gold Coast, said he did not know where the investigation was at. "It just goes on and on and on," he said. "I've been asking the police to hurry up. It's vexatious. I want to know why they're wasting time."
Horan denies the allegations. Peters kicked Horan out of NZ First when news of the allegations broke last year. Horan became an independent MP and will stand in the September election.
Relations have been frosty between the pair in past weeks, with heated barbs flying in Parliament. "All I've done is stand up against a bully. He's the one who has resorted to name-calling," said Horan.
Horan has made a series of allegations including:
- Peters' failure to declare a stake in a racehorse on his pecuniary interests file.
- NZ First used about $20,000 from its taxpayer-funded leader's budget to buy the Vanguard "constituent management software". Horan claims Vanguard is used to seek memberships and donations, against Parliament's rules.
-NZ First staff paid by Parliamentary Service are running the software, also against the rules.