Mr Samuels yesterday stood down from his ministerial duties for two weeks while Christchurch-based Detective Superintendent Jim Millar conducts a police inquiry.
Police Commissioner Rob Robinson said the inquiry was triggered by a letter from Act leader Richard Prebble to Prime Minister Helen Clark containing accusations of "historical sexual offending."
Helen Clark's handling of the affair came under fire in Parliament yesterday when it emerged she learned of allegations against Mr Samuels in January.
She said yesterday she was satisfied with Mr Samuels' denials, but believed the matter was best dealt with by the police once an "accomplished smear-monger" like Mr Prebble was involved.
Mr Samuels told Parliament he "absolutely denied" the "very serious allegations."
TVNZ's Holmes reported last night that Mr Samuels admitted to having had a relationship with the woman and that she had an abortion.
He insisted she was not under age at the time.
An uncle of the woman, Rodney Tregerthan, alleged last night she was under age when she went to live with Mr Samuels.
Between getting her driving licence at 15 and her passport at 16, the young woman fell pregnant to Mr Samuels.
She had an abortion at the Epsom Day Clinic in Auckland.
Afterwards, Mr Samuels made arrangements for the girl to meet her mother in a hotel carpark.
"He dropped her in the carpark, dropped her pack on the ground and drove off," said Mr Tregerthan.
"She started to haemorrhage, she went into the toilets, her mother found her and she got infected, unable to have kids."
Mr Tregerthan said Mr Samuels was made aware of the allegations against him in December, when the young woman's mother met him and an adviser.
The family tried to persuade Mr Samuels to establish a trust to pay for counselling for the woman.
"He was full of remorse and said the trust would be set up in 10 to 14 days," said Mr Tregerthan.
"Nothing happened."
The mother had also contacted other senior officials and Labour MP Chris Carter.
Mr Tregerthan said the mother's dealings with Mr Carter had not been handled well and had "almost bordered on extortion."
He said the woman had been reluctant to complain to police because she was afraid of what Mr Samuels might do.
Mr Tregerthan said he approached Mr Prebble and Television New Zealand on Monday because he felt he was not making progress with officials representing Helen Clark and Mr Samuels. He was acting in the woman's interests, and was not politically motivated.
In January, police diplomatic protection squad members became concerned at the mother's actions.
The head of the squad, Inspector Tom Stenhouse, and Mr Samuels spoke about the matters.
At the time, sources said, the woman did not wish to lay a complaint.
Police also had concerns about the credibility of the mother and decided the allegations had no substance.
In the meantime, continued threats caused police to hold fears for the safety of Mr Samuels, and they became concerned the mother would approach him at Waitangi during Waitangi Day celebrations.
They offered him protection, but he declined, saying the mother should be allowed to approach him because he had nothing to hide, sources said.
A lawyer acting for the daughter, Murray McKechnie, said last night that he did not wish to comment on the case.
Asked if she had made a complaint, he said: "I can't discuss the situation in relation to my client."
He would not say how old she was or when the alleged incidents occurred.
Mr McKechnie said he did not know where Holmes had obtained the information about her age.
"Everybody's problem at the moment is that nobody seems to know the facts. The facts are hard to find."
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