The couple had been convicted of tax evasion

Mr Singh, 43, was jailed for three and a half years and his wife, 44, was ordered to carry out 150 community service.

Their convictions were overturned because customs officers were found to have carried out an unlawful search of the couple's home.

The Court of Criminal Appeal in Edinburgh ruled that items taken during the search were inadmissable as evidence.

Officers had gone beyond their powers and invaded the Singh's right to privacy, the court heard.

Granted special powers

The judges ruled the seizure of documents from the couple's accountant was also illegal.

Lord Cameron said: "As with any other officials who are granted special powers to be exercised in the public interest but which involve interference with an individual's right to privacy, Customs and Excise officers must exercise their powers only within the limits which are granted to them."

"If they do not do so, then they act in excess of those powers and unlawfully," said Lord Cameron, who heard the appeal with Lord Macfadyen and Lord Weir.

Mr and Mrs Singh were originally prosecuted in a trial that lasted more than seven months and began in 1998.

The judges said the officers should have known of the warrant conditions

They had originally been charged with the fraudulent evasion of VAT totalling �167,030, representing suppressed sales at restaurants in Glasgow and Paisley of �1.25m.

They were eventually convicted of committing fraud for an "unknown sum" of VAT through the Amritsar and Shezan Tandoori restaurants in Kirk Road, Bearsden and Glasgow Road, Paisley.

Customs men had carried out observations at the restaurants to build up a picture of the trade carried out.

But the Crown case against the couple, who were sole partners in the businesses, crucially depended on material recovered by officers in a search of the Singh's home and books obtained from their accountant.

Procedures and safeguards

Lord Cameron said they were far from satisfied that it could be said that four extra officers had not taken part in the search.

He said the Singhs would not have known of the terms of the warrant and so could not have objected at the time.

However, said Lord Cameron, said the customs officers should have known of the restrictions.

The appeal judges said that the convictions of the couple must be quashed.

HM Customs and Excise said it has strict procedures and safeguards relating to warrants and officers are aware they have a duty to fully respect the rights of the individual.