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 that he could not discuss the issue.