National MP Mark Mitchell says he made off-the-cuff comments about Len Brown's private life which he did not believe amounted to warning the Auckland mayor that news of his scandalous affair was about to break.

The story of Mr Brown's extra-marital affair with aspiring politician Bevan Chuang continued to develop today, with Prime Minister John Key saying Rodney councillor Penny Webster passed on the tip to the Brown campaign.

Rodney MP Mr Mitchell today confirmed he had spoken with Ms Webster at a function where he made very generic, off-the-cuff comments about Mr Brown's private life which he did not believe was enough to warn the Brown camp that news of the affair was about to break.

He said even if he had known the detail, he would not have acted on them, saying "this sort of campaigning is not that nice anyway. It's always the collateral damage - it's always the families that end up getting hurt".


Mr Key said Ms Webster had rung him this morning after stories about a National MP tipping off the Brown campaign surfaced. She had told him the MP did not have many details and was simply gossiping.

"The way it was told to me, they didn't have any details, it was just rumour, and they were just gossiping to each other. Penny Webster then took that up with Len Brown," Mr Key said today.

He said it did not amount to a tip-off aimed at forewarning Mr Brown's team and even if it had, he would not have had an issue with it: "We've got nothing against Len Brown."

He maintained the National Party was not involved.

"I don't have any advice and I don't believe the National Party has been involved at all. There may be people who knew about it who are members of the National Party, or at least vague sort of details, but there are also many people who knew about it that weren't members of the National Party."

A source inside the Brown camp had also told the Herald that Ms Webster alerted them to the tip after hearing it from Mr Mitchell.

Ms Webster - a former Act MP and loyal supporter of Mr Brown, yesterday would neither confirm or deny passing on the tip to the Brown campaign when approached by the Herald.

Mr Mitchell didn't know Whaleoil was working on the story and had heard only vague rumours about Mr Brown.