Key Points:

National leader John Key has accepted MP Tim Groser's word that he did not smoke cannabis in Jakarta while he was New Zealand ambassador there in the mid-90s.

Mr Groser has admitted smoking cannabis, but rejects claims by his former wife, Milda Emza, that he smoked on the job. He says her claims have to be seen in the context of a failed marriage.

Mr Groser yesterday issued a public apology to her for comments he made to Paul Holmes that were reprinted in the Holmes Diary in the Herald on Sunday.

"I will take the comments of my angry and hurt ex-wife on the chin," Mr Groser's statement said. "They were a result of my ill-judged recently published comments, for which I unreservedly apologise to her."

Holmes wrote last month: "Tim's marriages have not been successful, as he frankly admits. He's had rather a tough time over the years. He says he has reached the point now that if he is attracted to a woman he has to assume there is something seriously wrong with her."

Mr Groser's former wife wrote to National Party president Judy Kirk with her allegations, the Sunday News reported. She said a friend brought cannabis for him some time before they were married in 1996.

Mr Groser said that in rejecting the story, "I want to be very clear that I make no claim to having led the full life of a choirboy when I was younger. I have made mistakes that I have learned from and which I regret.

"I admit to having used cannabis in my earlier life and do not want to hide that fact. However, I repeat that these specific allegations published [yesterday] are untrue."

Mr Groser became a Muslim to marry his second wife, an Indonesian Muslim. They have joint custody of a 10-year-old daughter.

He was ambassador to Jakarta from May 1994 until 1997 and resigned from a job as ambassador to the World Trade Organisation to stand for National in 2005. He has been fast-tracked to a caucus ranking of No 15, and is expected to be Trade Minister if National leads the next Government.

If the allegations were true, they would almost certainly mean the end of his political career. It would be considered gross misconduct of a senior public servant, regardless of Indonesia's strict drug laws.

Mr Key said he had asked Mr Groser directly about the story. "He has denied that there is any truth to those, and I accept him at his word."