National party leader Don Brash remarried four months after his divorce was finalised, his first wife, Erica Brash, says.

She has issued a statement in response to being asked for her reaction to Dr Brash's admission this week that he had an affair during their marriage.

Dr Brash's relationship with his now second wife, Je Lan Lee, has been widely publicised after his claim that Prime Minister Helen Clark was "indifferent" to the institution of marriage.

Erica Brash said she and Dr Brash had been married for 25 years when their divorce was finalised.

"Both Don and Je Lan Lee were married when they started their relationship and sought divorces as a result.

"They got married four months after Don's divorce was finalised. It was a painful time as these things usually are."

Dr Brash denied this week that he had been personally attacking Helen Clark, who has been married for 22 years, but was drawing attention to her previously reported questioning of whether people needed to get married at all.

He said he was not happy his affair had been reported, and said that was "grossly interfering" in his personal business.

The fact Dr Brash knew Je Lan Lee while previously married has been reported in the past.

In a feature article published about him this week he said the pair had met in 1982 while both were at the Kiwifruit Authority.

The relationship had not survived, he said, because they were both married.

Dr Brash was reported as saying after their marriages broke up that the pair were free to get together, but it was some years before they did.

"It was hard to forget her. I managed to find her and ... asked her to marry me," he told the magazine.

Senior cabinet minister Phil Goff said yesterday that the National Party leader's credibility was shot.

He said Dr Brash had tried to portray himself as a 'Mr Clean', above petty politics.

"He has destroyed that image for all time."