A drugs trial which lasted four months and is believed to have cost the taxpayer about £1million has collapsed in mysterious circumstances.

A judge ordered a jury at Bradford Crown Court to find Robert Blackburn and two co-defendants not guilty on charges relating to a police seizure of 10,000 ecstasy tablets.

Prosecutor Guy Kearl QC said a complex "legal" issue had forced him to offer no further evidence.

Mr Blackburn, 35, of Moorside Street, Low Moor, had denied conspiring to supply ecstasy and amphetamine to others.

He also pleaded not guilty to a third charge of conspiracy to offer for supply a quantity of fake amphetamine.

His co-defendants Gary Capitano, 37, of Moortown, Leeds, and Andrew Briggs, 39, of Illingworth, Halifax, had also pleaded not guilty to the conspiracy charges.

Mr Blackburn wiped his eyes with a handkerchief as the not guilty verdicts were read out by the foreman of the jury.

Afterwards he refused to comment on the trial.

The first five weeks of the trial, which began in May, were spent on legal argument. It collapsed yesterday as the prosecution was presenting its case.

Earlier in the trial Mr Kearl told the court that Mr Blackburn's Mercedes car had been bugged with a secret listening and recording device and that he had been spied on by surveillance teams.

He alleged that Mr Blackburn, who runs a decorating firm, bought a drug-making kit in Leeds to bulk out illegal substances the three were going to buy. He added that a bag containing 5,000 ecstasy tablets was later thrown from the car as they were being followed by the police and that another 5,000 were recovered from premises at North Street Farm in Thackley.

When questioned by police after his arrest Mr Blackburn denied that any bag had been thrown from his car. He claimed the police had fabricated the evidence.

Yesterday Mr Kearl told Judge Rodney Grant: "The prosecution has been giving considerable consideration over the course of the past week or so to certain issues. The reason that it has taken some time is that the issues are not straight forward.

"The result of that is that we will offer no further evidence against the defendants on each of the counts."

Afterwards a spokesman for the National Crime Squad said: "Following the development of a legal issue during this trial we have, after careful consideration of our position in consultation with the Crown Prosecution Service, decided to offer no further evidence against the defendants in this case."

Malcolm Taylor, a lawyer for the Crown Prosecution Service, said: "We have a duty to re-evaluate the case as it goes on and developments occur. For a number of reasons, including fairness to the defendant, we are unable to comment any further."

Three other people connected with the case are awaiting sentence after pleading guilty to conspiracy to supply ecstasy and amphetamines.