A Liberal Democrat MP accused of "inappropriate behaviour" towards a female constituent will not be charged.
Portsmouth South MP Mike Hancock, 64, was arrested on suspicion of indecent assault in October.
The Crown Prosecution Service (CPS) said the allegations centred on a series of visits the MP made to the woman's home between March and June.
A spokesperson said there was insufficient evidence to prosecute. The MP has always denied any wrongdoing.
Mr Hancock said: "I have always maintained my innocence over this. I have co-operated fully with police at all times and at all times vigorously contested these allegations."
He added: "I hope that this will draw a line under this for all concerned."
The CPS said it had received a file of evidence from police on 8 December.
Russian spy claims
A spokesperson said: "Mr Hancock has stated these visits were made in his role as an MP and not for any personal purpose.
"After thoroughly reviewing the file, we have concluded there is insufficient evidence for a realistic prospect of conviction, as there is no evidence to disprove Mr Hancock's account of the nature of the visits.
"We have written to the complainant to explain our decision and offered her a meeting."
Mr Hancock said he had offered help and support to the woman.
In a separate matter, the MP's parliamentary aide was arrested earlier this month over claims she is a Russian spy.
Katia Zatuliveter, 25, who worked for Mr Hancock, was arrested on 2 December.
In an e-mail sent to the BBC from the immigration centre where she was being held, Ms Zatuliveter vowed to fight any deportation case.