Mr Condit offered to take the lie detector test

But Washington Assistant Police Chief Terrance Gainer called the test "self-serving," because Mr Lowell had not worked with police to come up with questions and agree on an expert to administer the test.

According to Mr Lowell the politician answered "no" to each of the "three key questions":

• Did you harm Chandra Levy?
• Do you know where Chandra Levy is?
• Did you ask someone else to harm Chandra Levy?

"The congressman was not deceptive in any way and in fact had a probability of deception of one-hundredth of one percent in the questions that mattered," said Mr Lowell.

The police and Mr Condit's lawyers had been negotiating on the limits of the test since Tuesday, with the police pressing for no restrictions on questions related to the disappearance of Miss Levy.

DNA evidence

Mr Condit has also handed over DNA evidence to detectives and the FBI, which they will use in tests on blood found after a search of his apartment building earlier this week.

Meanwhile police said they had searched more than 70 vacant buildings in the Washington DC looking for Miss Levy, who was last seen 30 April.

Captain Willie Smith said officers, with sniffer dogs trained to find bodies, were trying to get through 100 buildings in the neighbourhood near Misss Levy's apartment.

"We just want to make sure all the bases are covered," he said.

Lack of leads

The police conceded it was a lack of good leads, rather than specific information, that led them to look at abandoned properties as places where someone could have left a body.

Miss Levy was last seen in April

Police say they are pursuing a number of theories about Miss Levy's disappearance, but that they have ruled out suicide since so much time has passed and no body has been found.

Authorities now plan to release simulated images of Miss Levy with different hair styles.

Not a suspect

Police have said repeatedly they do not consider Mr Condit a suspect in Miss Levy's disappearance.

A police source said the congressman had now acknowledged a romantic relationship with the former Bureau of Prisons intern, despite denials from his office.

The congressman, who is married with two grown-up children, had until then insisted the young woman was merely a friend.

It was Miss Levy's mother who first suggested Mr Condit take a lie detector test, saying she did not believe he had shared with police all he knows about her daughter.