The National Party is being highly critical of Jacinda Ardern's handling of accusations against a former Labour Party worker.

A 19-year-old volunteer is now accusing the staffer of sexual assault.

The Prime Minister has stated she is concerned and frustrated by the process, and by the nature of the allegations.

The Labour Party investigated seven formal complaints about the man earlier this year, but decided no disciplinary action was warranted.

National's deputy leader Paula Bennett says a man working in the Prime Minister's office has been accused of sexual assault, bullying and intimidation.

Paula Bennett told Mike Hosking victims feel let down by a leader they thought would be championing all women's rights.

She says at every turn they've been more than dismissed, which has been re-traumatising for them.

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