Scotland Yard is to examine allegations that a child sexual abuse ring was connected to a Downing Street aide.
The Metropolitan police commissioner, Bernard Hogan-Howe, said on Monday the claims would be treated seriously.
Last week the Labour MP Tom Watson used parliamentary privilege to make the allegations. It is understood they relate to a previous prime ministerial aide and not to anyone who has recently served in Downing Street.
Hogan-Howe said a senior officer would look at the claims and that police were in contact with Watson to see if he could provide detectives with more details.
He said they would ask the Labour MP this week “what his sources are and if they are prepared to talk to us” as the police assess the strength of the allegations.
Last week Watson told MPs that a police file relating to Peter Righton, who was convicted in 1992 of importing child abuse images from the Netherlands, needed to be re-examined.
“The evidence file used to convict Peter Righton, if it still exists, contains clear intelligence of a widespread paedophile ring,” Watson said during prime minister’s questions. “One of its members boasts of his links to a senior aide of a former prime minister, who says he could smuggle indecent images of children from abroad.
“The leads were not followed up, but if the files still exist, I want to ensure that the Metropolitan police secure the evidence, re-examine it and investigate clear intelligence suggesting a powerful paedophile network linked to parliament and No 10.”
Watson gave more detail on his blog. He said he had been contacted by a former child protection specialist who was concerned that not all of the leads the police had when investigating Righton were pursued. “The contact, who has seen the letters, claimed that one paedophile in particular was of great concern. He said that the paedophile, who worked with children, boasted of a key aide to a former PM who could help get hold of indecent images of children,” Watson wrote.
The allegations come amid concern over the scale of abuse allegedly perpetrated by the radio and television presenter Jimmy Savile.
Hogan-Howe said the police and other institutions had missed the opportunity to collate allegations against Saville. “Organisations including the police have had individual allegations that have not been put together to actually show that this person may well have shown a pattern of behaviour that’s been pretty awful,” he said.
He added that the allegations against Savile dated to the 1960s and spanned more than half a century. “You might have thought that people would at least have talked about it and intervened,” he said. “It does look as if from time to time people have been concerned, they’ve made the start to intervene, but probably then they’ve relied a little bit too much on his reputation and his word that he did nothing.
“If you accept all the public accounts of the activity, then it’s possibly spanned 50 years, which is a huge amount of time.”
The Met’s Operation Yewtree is investigating claims from 300 potential victims dating back decades. It became a full criminal investigation when detectives determined there could be people still alive who were allegedly involved in some of the abuse.
On Sunday the former pop star Gary Glitter, whose real is name Paul Gadd, became the first person to be arrested as part of the operation. He was later bailed.
As of last week, detectives had recorded 114 alleged crimes of sexual assault and serious sexual assault. Most alleged victims name Savile as their attacker, but the allegations also involve other individuals from a number of institutions.