Hannah Hewitson swapped council houses with the convicted murderer in March 1991, just a month after Vicky Hamilton disappeared in the town.

The 49-year-old mother said that an officer called at her new home in Robertson Avenue to ask if she had seen the missing 15-year-old schoolgirl.

Mrs Hewitson said her husband, Peter, 52, let police search their garden shed as part of the hunt.

Police chiefs have always maintained that there was no record of Robertson Avenue being visited during the initial door-to-door inquiries.

The claim comes after it was revealed in the Evening News detectives from Portsmouth issued an appeal to Lothian and Borders Police in August 1993 that Tobin was a wanted sex attacker who had lived in the West Lothian town but police did not link Tobin's time in Bathgate with Vicky's disappearance.

Tobin exchanged his council house with Mrs Hewitson's home in Irvine Drive, in Margate, Kent, only weeks after the schoolgirl vanished.

Tobin, 62, now faces spending the rest of his life behind bars after being jailed for at least 30 years for abducting, sexually assaulting and murdering Vicky.

Mrs Hewitson, 49, who now lives in Maidstone, said: "We moved in during March and I remember it was within a three-month period from that. We had come back from shopping.

"We had only been back for about 30 minutes when there was a chap at the door and it was a policeman standing with his clipboard.

"That was the first time I heard Vicky Hamilton's name. He said he was doing door-to-door inquiries and asked had we seen Vicky. He also asked if we had a garage or a shed and could he have a look in it. My husband took him to the shed and let him have a look.

"We told him that we had done an exchange. We moved from Margate to Bathgate and Mr Tobin was in the move."

Mr Hewitson, a warehouse worker, told the trial at Dundee High Court that he and his wife and family exchanged the tenancy with a man named Peter Tobin, but said they never met.

Today Edinburgh Pentlands MSP and former Scottish Tory leader David McLetchie said the failure to make the link between Tobin and the missing Vicky in 1993 raised questions about co-ordination between police forces.

"It's disappointing this link was not made, and a connection which, with the benefit of hindsight, looks obvious was not made, with potentially tragic consequences for later victims of Tobin," he said.

"It raises the question whether, when one force says 'Can you look out for this person?' is it logged, monitored and followed up on beyond the initial message? Does anyone follow it through in a co-ordinated way?" He added: "One would like to think that kind of tip-off would be handled better today than it was at the time."

A Lothian and Borders Police spokesman said: "There is no record of Robertson Avenue being included within the initial door-to-door inquiries."

The force also issued a statement praising the work of officers who brought Tobin to justice, saying: "Officers from Operation Mahogany can feel justifiably proud of their involvement and years of commitment in this case.

"This is a time to reflect on a young and promising life so cruelly taken."