Officers are also investigating the possibility that the couple had specially targeted Lucien Lawrence.
His mother, Mrs Frances Lawrence, 47, has told detectives that the couple, who claimed to be social workers, asked for Lucien by name.
Detective Inspector Alan Gale said yesterday outside the Lawrence family's home in Ealing, west London: "Police are currently investigating an allegation of attempted abduction of Mrs Lawrence's son from this address on Wednesday afternoon.
"Shortly after 3.30 a man and a woman came to the front door of the house, said they were from social services, and asked to take Mrs Lawrence's son to the local health centre, apparently for a check-up.
"She was suspicious and refused them access to her son. She made inquiries to her local doctor and contacted the police. They used her son's name. I can't say whether this is a specific attempt against Mrs Lawrence or an ad hoc attempt."
Mrs Lawrence stayed inside the smart detached house all morning, giving a statement and details of the attackers to CID officers. Mr Gale said: "Mrs Lawrence is obviously very upset with this incident and I would ask that the media respect her privacy at this traumatic time."
In September, mother-of-four Mrs Lawrence disclosed that she was being terrorised by a hooded stalker.
But police said there was no evidence to link the stalking to the abduction attempt.
Mrs Lawrence spent yesterday helping police draw up E-fit pictures of the two suspects.
She told police the man was aged about 40, 5ft 11in tall, with short brown hair and black-rimmed glasses, and was wearing a beige mackintosh.
The woman was aged about 28, black, 5ft 6in, with short, black, bobbed hair, and was wearing a black jacket and black shirt.
Mr Gale said: "Any allegation made of this nature we will treat very seriously."
Detectives took Lucien to school this morning because of the media interest in the case.
Officers are also investigating whether the incident could be linked to any similar attacks in the west London area.
As the investigation continued yesterday the Home Office announced it was launching an award scheme in memory of the murdered headmaster.
Michael Howard, the Home Secretary, said he hoped the Philip Lawrence Memorial Awards would "help raise the sights of young people".
Mr Lawrence's widow Frances welcomed the news, saying she and their children had been profoundly moved by the award plans.
Mr Howard was giving further details of the awards which he proposed in October, after Mrs Lawrence launched her own call for good citizenship to be promoted.
Mr Lawrence was stabbed to death outside St George's School, Maida Vale, west London, after he tried to protect a pupil from a 15-year-old boy from another school.
Today's announcement came two days before Mr Lawrence's nine-year-old son Lucien unveils a plaque in front of the school gates to mark the first anniversary of his father's death.
The Home Office said the awards scheme would be launched in March next year, when nominations would be invited so that the first awards could be made around the second anniversary of the murder.
"The awards will focus on young people's achievements in, for example, combating lawlessness and violence, promoting racial harmony and encouraging good citizenship," a spokesman said.Reuse content