(Adds John Key press conference)

Wellington, June 4 NZPA - National MP Richard Worth's future in Parliament is in doubt as police investigate a serious allegation against him.

Prime Minister John Key accepted Dr Worth's resignation from Cabinet last night and Wellington police today confirmed they were conducting a preliminary investigation.

What allegations Dr Worth faced were not being revealed, by either police or the prime minister.

"All I can tell you is his conduct does not befit a minister and I will not have him in my Cabinet," Mr Key told a press conference this morning.

"If he hadn't resigned I would have sacked him."

Dr Worth, who remains an MP, said in his brief statement he deeply regretted resigning.

"I am resigning from the role for personal reasons," he said.

"It has been a privilege to have been a minister in this government. I will not be making any further comment to the media."

Mr Key said an outside party had informed his office of the allegation of a "relatively recent" incident last week.

Dr Worth had not come to him about it.

Dr Worth has been given a two-week leave of absence from Parliament: "because I think he needs some time to reflect on his future and whether he intends to stay as an MP".

Mr Key said it was up to Dr Worth to decide whether to leave Parliament, but if police laid charges he may be suspended or expelled from Caucus.

`Ultimately whether he stays as a member of parliament is a matter at this point for him to consider.

"I urge him to consider his own future, and take counsel with his own family and friends.

"It may be in the fullness of time he is not appropriate to be a member of parliament. But that is not something I can adjudicate on at this time."

Dr Worth has been at the centre of a number of judgement lapses that have shunted him into the media limelight.

Mr Key said the resignation had nothing to do with those.

"The decision that has been reached today has been reached on the back of this incident and nothing else."

There were "a number of reasons" why Dr Worth had lost his confidence.

Dr Worth was a minister outside cabinet holding the portfolios of internal affairs and land information.

He was also an associate minister of justice.

Dr Worth's ministerial responsibilities had been temporarily transferred to Maurice Williamson.

Mr Key said he would permanently reallocate them in "the near future".

He was the first minister to resign in the new Government, elected last November.

Dr Worth was reprimanded by Mr Key in April over a potential conflict of interest on a trip to India. He made other gaffes but none were serious.

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