Police are speaking to several people linked to the National Party's Clutha-Southland MP Todd Barclay following an alleged employment dispute.
Parliamentary Service, which employs some of Mr Barclay's staff, have also been approached by police.
Two staff members, electorate agents Glenys Dickson and Barbara Swan, resigned this year.
Ms Swan confirmed to the Otago Daily Times yesterday that police had arranged a meeting with her.
She is currently working out her notice period in Mr Barclay's Queenstown office.
She had "no idea" what police wanted to discuss.
Electorate chair Stuart Davie also resigned this year, saying his position was "untenable".
A Parliamentary Service spokeswoman confirmed that the organisation had been approached by police in relation to Mr Barclay.
She would not comment further, saying it would not be appropriate.
A police spokesman would not confirm whether a complaint had been laid, saying he could not comment on individual cases.
But it is understood that at least two current or previous employees in Mr Barclay's electorate office have been approached by police.
The police involvement is believed to be related to allegations that the first-term MP made a secret recording of a staff member.
Prime Minister John Key backed Mr Barclay this week, saying that he had seen no evidence that he had done anything wrong.
Mr Key said he had spoken to the MP.
National Party president Peter Goodfellow also said he backed Mr Barclay.
The 25-year-old MP entered Parliament in 2014, taking the seat which Bill English had held for more than 20 years.
He said earlier this week that filling Mr English's shoes had been a huge learning curve and he had "made some mistakes".
Mr Barclay said this afternoon that he could not discuss the issue.
He confirmed that he had not been contacted by the police in relation to any complaint.
"If they do contact me regarding any matter, then I will co-operate fully."