Dr Worth was embroiled in a sex scandal when a Korean businesswoman laid a complaint against him and another incident was revealed involving a woman member of the Labour Party.
At the time he was minister of internal affairs. He resigned the portfolio on June 3 after Prime Minister John Key said he had lost confidence in him, and quit Parliament on June 12.
It was reported in July that the Korean businesswoman, who was never identified, had dropped her complaint, which was not confirmed.
Inquiry head Detective Inspector Paul Basham said police had completed a "careful and thorough investigation into the matter", which included peer review by a senior CIB officer and assessment by police legal advisers, the New Zealand Herald website reported.
A spokesman added: "Having completed the investigation, the police have determined that there is no basis for proceeding with any criminal charge against Dr Worth."
Police interviewed Mr Worth in Auckland in June.
After the sudden announcement of Dr Worth's resignation as a minister in June, Prime Minister John Key said that he would have sacked him had he not resigned.
"His conduct does not befit a minister, and I will not have him in my Cabinet," Mr Key said at the time.
He also said then that he would probably reveal why he had lost confidence in him but he did not want to contaminate a police investigation. He later said he would not comment on the issue.
