The National Party Leader Don Brash is taking time off to spend with his family because of difficulties in his marriage.

In a brief statement, Dr Brash said: "Je Lan and I are working through these difficulties and we are both committed to making our marriage work.

"As people will understand, this is a very difficult time for me and my family. I ask that the media respect our need for privacy."

The statement, shortly after lunchtime today, came after mounting speculation spurred by a story in the Independent Financial Review that Dr Brash had faced questions on his personal life at a National party caucus yesterday.

It also follows threats in Parliament last week by Labour MPs to lift the lid on National MPs' personal lives, with some comments directed personally at Dr Brash.

NZPA understood Dr Brash was challenged at the party caucus meeting on whether he had anything to hide.

It is understood he refused to talk about his personal life, but said he had not misled the public.

Dr Brash's spokesman would not comment on whether the leave was in any way related to yesterday's caucus. He said the National leader was expected back at work on Friday.

The Independent Financial Review weekly newspaper today ran a frontpage story about the caucus showdown.

Dr Brash has previously said he fell in love with Je Lan in a case of love at first sight when they met in the 1980s at the Kiwifruit Authority.

His biography, by Paul Goldsmith, describes how he was fascinated by his highly competent secretary from Singapore.

He began an affair with her, and Lee left her husband in 1983. Brash left wife Erica in 1985. In 1989, Dr Brash and Je Lan were married.