Police are examining if former No 10 chief of staff Jonathan Powell potentially perverted the course of justice by advising a republican terror suspect not to return to the UK, a Westminster committee has heard.
A senior Metropolitan Police officer told MPs that the PSNI was checking the claim to assess whether a formal criminal investigation should be launched.
Conservative MP Oliver Colvile had contacted police in London and Belfast about the matter after Mr Powell, Prime Minister Tony Blair's right-hand-man in Downing Street, referred to the episode while appearing before the Northern Ireland Affairs Committee last month.
While giving evidence to the committee's inquiry into a Government administrative scheme to deal with on-the-run republicans, Mr Powell was asked about his encounters with Rita O'Hare around 14 years ago.
Ms O'Hare, Sinn Fein's representative to the United States, is one of the most high-profile fugitive republicans, having skipped bail to the Republic in 1972 after her arrest in connection with the attempted murder of a soldier.
Mr Powell was quizzed by Mr Colvile on a comment he had made during a meeting with Sinn Fein to the effect that Ms O'Hare should not travel to Belfast as it might result in her arrest.
Explaining why he had told her not to return, Mr Powell had told the committee: "Had she come back, been arrested feeling she had fallen into a trap by me trapping her into coming back, the peace process would have been dead - it would have been a very bad idea."
The Met's Assistant Commissioner for Specialist Operations Mark Rowley was giving evidence to the committee inquiry yesterday and Mr Colvile asked him for an update on his query.
"As is routine practice if we get allegations that pertain to potentially different jurisdictions, we have had a conversation about which force is best placed to deal with it and the conclusion we came to is the PSNI are looking at that," the officer said. "At the moment they are seeing whether there is sufficient evidence to merit going into a formal criminal investigation or not."
Former US Senator Gary Hart will arrive in Belfast later this month as the latest in a decades-long parade of special US peace process envoys - and a man long off the radar of mainstream American political life.