Labour MP Darien Fenton has publicly apologised for her comments about the Mad Butcher Sir Peter Leitch and offered to shout him a beer to make up for it.

On a posting on Labour's Red Alert blog late last night, Ms Fenton said her comments on Facebook had caused "a bit of a media kerfuffle".

"Normally this kind of fuss wouldn't bother me much, but I've had another look at what I said and reckon I went too far."

She said Sir Peter was "a top bloke" and had done a lot for communities.

"Even though we might disagree on politics these days, I've still got a lot of respect for him.

"So, Peter, if you are reading this, sorry about the comments. Oh and we should catch up for a beer sometime - my shout. Enjoy the game at the weekend."

The apology was over comments she made on Monday following Sir Peter's endorsement of Prime Minister John Key on Radio New Zealand.

Ms Fenton posted on her Facebook profile: "So, Mad Butcher. You have a choice, but so do I."

When others asked Ms Fenton to explain, she called Sir Peter a sycophant and said: "[He was] sucking up to John Key big time. I'm never going near him again."

Ms Fenton said she was upset Sir Peter had been complimentary towards Mr Key and that the Mad Butcher had invited the Prime Minister to join him to watch the Warriors play at Sunday's NRL grand final.

Labour leader Phil Goff said today he did not agree with Ms Fenton's comments about Sir Peter.

"I'm a real Warriors fan. I've been going to their matches for years and have caught up with the Mad Butcher many times. He is a great guy and a great ambassador for rugby league. He is absolutely entitled to express whatever opinion he likes. Go the Warriors against Manly."

Sir Peter said from Melbourne yesterday that he did not know what to say when he heard what Ms Fenton had said about him.

"I honestly don't know what to say, to be fair - and it's not often that I'm lost for words. I don't know what I've done wrong.

"I'm very disappointed and it's just taken the wind out of my sails. I'm absolutely gutted by her comments."

Sir Peter said he supported Helen Clark when Labour was in power and took her to Warriors matches.

"The National Party never complained that I supported Helen Clark," he said.

"I've done nothing with John Key that I didn't do with Helen Clark - I've been a little bit more vocal."

In response to Ms Fenton's claims that he was "sucking up to John Key big time", he said: "I thought freedom of speech was one of the things people went to Gallipoli for. But obviously in her opinion, it's not."

He also said it was unfair that she was taking her frustrations out on the 37 Mad Butcher stores which he sold in 2007, but still promotes.

Ms Fenton said she made the comments in the "heat of the moment" after hearing Sir Peter compliment Mr Key - but was adamant she was not calling for a boycott of the butchery chain.

"I have never ever suggested a boycott, or started a boycott or called for a boycott - that is simply not true."

Ms Fenton has since shut her Facebook profile down.