A secret recording released last week during a row featured opposition and National Party leader Simon Bridges describing one of his own MPs as "f***ing useless".

While Mr Bridges has since apologised for his comments, it hasn't saved him from a finger-wagging from his mother.

"I was disappointed Simon used bad language," Ruth Bridges told the NZ Herald.

"He certainly wasn't brought up that way, but I suppose he was trying to be blokey amongst the blokes".

Mrs Bridges also described the difficulty of reading hurtful comments about her son.

"They love to say things like 'Simple Simon', 'you're a muppet'. It's upsetting and you feel the pain, but you get numb to it. There's nothing you can do about it," she said.

Her comments come after the mother of the MP insulted in the tape, Maureen Pugh, came to her daughter's defence.

"[Mr Bridges] really must be a dumb arse as my daughter is a hard worker for National, she got more votes for them than any other Nat on the West Coast and to call her useless is insulting and a lie," June Brigg said in a letter to Newshub last week.

Ms Pugh herself says she's accepted Mr Bridges' apology.

Mr Bridges, 42, is a former Crown prosecutor and government minister who in February became leader of the National Party.

Australian Associated Press