Simon Bridges' mother says she didn't bring her son up to swear, following his explosive assessment of his West Coast-based list MP's abilities.

The National party leader called Maureen Pugh "f***ing useless" in a recorded conversation released by rogue MP Jami-Lee Ross during a week of sex, revelations and leaked audio tapes.

Bridges' mother Ruth, 80, told the Herald on Sunday at her home in Tauranga : "I was disappointed Simon used bad language. He certainly wasn't brought up that way but I suppose he was trying to be blokey amongst the blokes".

Pugh's mother, June Briggs, lashed out at Bridges, describing him as a "dumbass". Ruth said she understood how Briggs felt from a "mother's point of view" but was happy her son had apologised to the MP "profusely".

The retired former primary school teacher says it was hurtful reading nasty 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.

"I would not respond. It would not be appropriate. It would create a bigger furore if you did."

The Opposition leader's mother was also upset her son was vilified following Ross' comments about the ethnicity of those on the National Party list.

The same recording revealed Ross saying to Bridges: "Two Chinese would be more valuable than two Indians".

"All the parties do it," Ruth said.

A young Simon Bridges with his parents Ruth (right) and Heath Bridges. Photo / supplied

"They are trying to get a balance of representation of different people in parliament. We have lovely Indian folk here who are very supportive of Simon. He has a great relationship with them. He's not in the least racist. It really upset me when they started on that."

But politics is off the the table whe it comes to mother and son conversations - when Ruth text Bridges out of concern this week he replied, "Mum I don't need your advice on politics".

"Simon doesn't talk politics with me – he just wants me to be his mum, but I do follow him extremely closely. You know if he hurts. I hurt. If he gets kicked. I feel the pain, naturally. I know he is a very good person, very genuine and he's scrupulously honest."

Ross went on medical leave from Parliament last month before he was identified in a report as the likely leaker of his leader's expense records - a finding he denied.

Ross then released recordings and texts as evidence of what he calls electoral fraud by Bridges, and passed the information on to police.

Two women have admitted affairs with Ross, while two others allege he harrassed them. Ross denied harrassment but apologised to the four women yesterday and admitted the affairs. One of the women is an MP.

Ross also apologised to his wife Lucy Schwaner, who Ruth said she felt for.

"That extra-marital affairs thing must be terrible for her. I hope Jami-Lee gets some medical help."

She says her son's marriage is rock solid.

"Simon has a very strong Christian faith and so does Natalie – they are really tight I have not had the slightest hint of anything going wrong. I know it's not part of his nature he's been brought up with strong values in those areas."

Ruth, who met Ross at a coffee meeting in Tauranga about four years ago, said she believes he may have had his nose out of joint when he was demoted and replaced by Barbara Kuriger as whip of the National party.

"Jami-Lee had his own agenda, he's incredibly mixed up – this has been a planned campaign by him which has been pretty bizarre and sad. He obviously has his own personal problems. There are a lot of big egos, a lot of ambition and a lot of jealousy.

"This one just turned toxic and the fact he had been recording the conversations over a period of time is such a horrible thing to do. These are conversations you have with mates and you don't expect them to be recorded and used against you."

She supported her son's inquiry into who leaked his expenses to the media.

"Simon is smart and has good judgement. A lot of people said he should have let it go, he's dug himself a big hole, but the reality is if you have got a snake you have to'smoke him out. That's why I think he's been vindicated in that regard."

And she's not worried about further recordings coming out.

"There may be a few more that might not be too edifying for Simon but wouldn't you hit with the best ones first to make an impact?"

Ruth concedes Ross' revelations have injured the National Party but says "it's not a lasting wound" and is confident her son will lead them into the next 2020 election.

"Hopefully they will see he is not at fault... whoever was the leader of the National party now, it would be really tough. Jacinda is the princess and very popular. The word opposition means to oppose -so it's a negative thing".