Prime Minister Helen Clark last night bitterly condemned all political smear campaigns after her husband, Professor Peter Davis, became the latest victim.

She dismissed suggestions her husband was gay as "complete and utter drivel".

She also condemned as "farcical" a suggestion that Professor Davis was detained by officials on a trip to the United States and had to be extricated by New Zealand foreign affairs officials.

"They are both completely baseless but the other one ... If anyone can seriously think you could have your husband smuggled out via MFat [Ministry of Foreign Affairs and Trade] from a foreign country without anybody ever knowing about it ... I mean please, it's just so farcical.

"But it is all farcical."

Helen Clark blamed the National Party for circulating the rumours.

National vehemently rejected the claim and offered its sympathy to her.

Helen Clark refused to comment on speculation that political enemies in the religious right had hired private detectives to follow her and her husband in a bid to find scandal.

But she condemned for the first time one of her senior ministers, Trevor Mallard, for his threats 12 days ago during crossfire over election spending to reveal secrets of MPs' private lives.

Mr Mallard made the first public reference in Parliament to an affair between National leader Don Brash and businesswoman Diane Foreman.

Helen Clark said last night: "Trevor went off the deep end. I don't condone it. I condemn. I condemn all those personal attacks."

Newspapers yesterday ran rumour stories about Professor Davis based on the publication today of Ian Wishart's Investigate magazine, which has run several stories this year about him.

The magazine invites readers to identify a man who embraced and kissed Dr Davis when he arrived at Labour headquarters on election night.

The man was one of the couple's oldest friends, Dr Ian Scott, who is gay.

Helen Clark said the suggestion that her husband was gay was "lies" and "an outrage".

Asked what she could do about the smear campaign, she said: "In the end you have got to run on your reputation. You have got a 25-year marriage, a happy marriage. You've got a good and close circle of friends and you just have to rely on people's common sense. This is complete and utter drivel.

"Everyone who knows Peter and myself will dismiss it. So I'm not wasting my time getting upset about it.

"It is the sort of smear that the National Party has tried to run from time to time in the 25 years I have been in Parliament."

She was "absolutely certain" the latest campaign originated with National.

"I have had feedback for weeks and weeks and weeks now from friends and friends of friends who've rung friends about people retailing these rumours and smears."

Helen Clark said National had been "furiously peddling" the claim that she had condoned Mr Mallard's threat because she had declared war on the election spending issue.

But when she had declared war, what she had in mind was to "put the blowtorch on their spending".

"It was never about a personal attack."

She said her heart sank when she saw news reports of Mr Mallard's threat to dish the dirt.

"Trevor's behaviour had absolutely no basis in any Labour strategy whatsoever."

National deputy leader Gerry Brownlee said the party was "comforted" by her public admonition of Mr Mallard, but rejected her claim National was behind the Professor Davis smears.

"If any of our members are involved in this sort of activity, then once they are found out they will be dealt with very severely."

He said yesterday's newspaper reports were disgraceful.

"I understand the Prime Minister would naturally be very hurt by that, and I have sympathy for the feelings she is having," Mr Brownlee said.

"What needs to happen now is that everyone draws a deep, deep breath and steps back a considerable distance and leaves people's private lives and families out of politics."