Senior members of Scotland Yard showed poor judgment in their handling of Britain's phone hacking scandal, the country's police watchdog said Thursday, in a further indictment of the U.K.'s most important police force.

The watchdog said senior officers in the London police force broke the rules when they hired former tabloid executive Neil Wallis to help run public relations and helped Wallis's daughter get a job.

Wallis was one of the first people arrested in the scandal over phone hacking at the now-defunct News of the World newspaper. His close ties to Scotland Yard — which long refused to properly investigate the practice — have badly dented the prestigious police force's reputation.

The Independent Police Complaints Commission's Deputy Chair Deborah Glass said that police should have known as long ago as 2009 that there was a problem with employing Wallis.

"Senior people appear to have been oblivious to the perception of conflict," Glass said. "It is clear to me that professional boundaries became blurred, imprudent decisions taken and poor judgment shown by senior police personnel."

The phone hacking scandal first boiled over in 2006 following the arrest of News of the World private investigator Glenn Mulcaire and senior journalist Clive Goodman.

The pair were convicted in 2007, and police later insisted there was little or nothing more to the story. There'd been only a handful of victims, the force said. There was no evidence anyone else was involved, it claimed.

In fact, there was ample evidence suggesting wide-scale malpractice involving hundreds of high-profile victims. At the same time Wallis was working for the police, senior officers were fighting to prevent the evidence from leaking to the public, forcing those who feared they'd been spied on by the News of the World to sue for a chance to see whether they had been targeted by the paper.

The police's dismissive attitude toward the scandal changed after revelations in the Guardian and The New York Times made it clear that the evidence of wrongdoing had been overwhelming all along. Three top police officers resigned, and a judge-led inquiry is now weighing whether the senior officers got too close to the press.

Wallis was arrested in 2011 but is out on bail and has yet to be charged.