Scotland Yard has confirmed it has credible evidence that a Peterborough councillor had a sexual relationship with a teenager while he was working as an undercover policeman.
Andy Coles met the 19-year-old woman when he infiltrated an animal rights group in the 1990s. At the time, he was 32.
The woman, known as "Jessica", has previously complained Mr Coles, and what she sees as his deception, to the Metropolitan Police. They investigated whether criminal charges should be brought against Mr Coles, but have confirmed that this will not happen.
"Jessica" told ITV Anglia: "I'm pleased the complaint has been upheld, but I'm disappointed there seems to be no accountability for the police at all.
"Coles was allowed to resign in 2013 and this was around the time all these revelations were coming out about what the undercover officers had done.
"They've said, were he still employed, there would be a case to answer for misconduct."
Coles' past as an undercover police officer came to light when his brother, Reverend Richard Coles, referenced it in his autobiography.
He described how his brother had led a double life, while his wife and baby daughter made do with unpredictable visits.
Mr Coles' alleged relationship with "Jessica" while he was undercover is under scrutiny from the undercover policing inquiry.
Otherwise known as the Pitchford Inquiry, it began in 2015 following claims an undercover police officer had infiltrated the family and friends network of murdered teenager Stephen Lawrence.
Other investigations revealed officers had had relationships with women while undercover - "Jessica" claims she was one of these women.
On its website, the undercover policing inquiry says "the first evidence hearings are expected to begin in June 2020, running from 1-19 June and 1-18 September 2020."
"Jessica" told ITV Anglia the chair of the inquiry has said both her and Coles will have to give evidence at a hearing.
"Jessica" said. "I think there are a lot of questions that need to be answered. Hopefully, we will get it from the inquiry."