A leaked email shows the National Party has widened its investigation into who leaked Opposition leader Simon Bridges' travel expenses.
The email shows National staff were told on September 25 the investigation will include those who don't work in Parliament.
"The scope of the PwC review, for completeness, now also includes all National MP's [sic] out of Parliament member support staff," the email informs staff. The word 'all' is underlined.
Investigators will be looking for "two specific documents and related emails accessing and/or referencing either/both of these two documents".
They are also focusing on communications with a specific phone number.
The email acknowledges it "may be an unsettling time", and reminds staff counselling is available through an independent third-party organisation.
The investigation period for MPs is from February this year - when the National Party leadership contest began. Staff communications will be investigated from August 1 until August 28. Newshub broke the story of the expenses on August 13.
Consent to the data or a waiver isn't necessary, because the staff are employed by Parliamentary Services, the email said.
Newshub requested an interview on the email with either Simon Bridges or deputy leader Paula Bennett. Both requests were declined.
PwC and Simpson Grierson are leading the investigation into the expenses leak, and it is being paid for by the National Leader's Office.
Newshub's political editor Tova O'Brien was leaked Mr Bridges' expenses on or before August 13. The information showed Mr Bridges had spent $113,973 on travel and accommodation during his road show.
A parliamentary inquiry was called by Speaker Trevor Mallard, who later cancelled the investigation, saying evidence showed it was a matter for the National Party.
Someone claiming to be the leaker sent a text to Mr Mallard, Mr Bridges and Newshub calling for the inquiry to be stopped due to ongoing mental health issues. Mr Bridges decided to continue with the inquiry.
In response to this story, a National party spokesperson said the scope of the inquiry has not been widened.
"It was always intended to include all MPs and staff who had access to the information and was intentionally broad to provide the greatest chance of finding an answer.
"In relation to the email, the terms of reference relating to staff are actually more narrow, with a shorter time frame than MPs. The email from Parliamentary Service was sent when discussions around the time frame were finalised and the provision of staff information progressed."