The credibility of the police investigation into alleged corruption in football received another blow today when Harry Redknapp proved in court that police who raided his house were acting unlawfully.

In a judicial review hearing, Redknapp and his wife challenged a decision by City of London Court to issue the warrant, and its execution by City of London Police. The court quashed the warrant and ordered City of London Police to pay £1,000 damages to Redknapp and part of his legal costs. Lawyers argued that, for legal reasons relating to the nature of the material being sought by the police, the City court had had "no power" to issue the warrant.

A total of nine people are on bail in connection with a continuing police inquiry involving searches at a number of football club premises, including Portsmouth.

Redknapp and Peter Storrie, the Portsmouth chief executive, were among five men arrested on suspicion of conspiracy to defraud and false accounting. The others were Milan Mandaric, the former Portsmouth chairman and now Leicester City owner, Willie McKay, a high-profile agent, and Amdy Faye, who is on loan to Rangers from Charlton Athletic.

The inquiry is believed to centre on Portsmouth’s signing of Faye from Auxerre for £1.5 million four years ago. After his arrest Redknapp was confident that he would be cleared of any wrongdoing. “We all helped the police with their inquiries, but it doesn’t directly concern me,” he said. “It’s other people involved. I think that’s the end of it.”

Nine people have been arrested in connection with police inquiries, most recently David Sullivan, the co-owner of Birmingham City, and Karren Brady, the club’s chief executive. Sullivan has described the investigation as “a huge waste of police time and money” and is furious that he and Brady have been dragged into an affair that he believes centres on the allegations not connected with the club.

“They started off looking for bungs,” Sullivan said. “Having found none, they’re now looking for anything to justify their time. There is no suggestion that anybody at Birmingham had any improper payments.”

The reputation of the City of London police force - it claims to be the country’s elite antifraud unit - was damaged last December after the collapse of the race-fixing trial of Kieren Fallon, the six-times champion jockey.