When a senior detective re-opened a notorious murder inquiry, the suspects were able to intimidate his wife and family with the help of an executive at the News of the World, the Leveson inquiry has been told.

Making one of the gravest Leveson allegations so far, former Crimewatch presenter Jacqui Hames, the then wife of Detective Chief Superintendent Dave Cook, broke down in tears as she accused the paper's then editor Rebekah Brooks of covering up the real reason why her family were targeted.

The intimidation was carried out after an offer of a £50,000 reward on Hames's Crimewatch programme for fresh information on the murder of Daniel Morgan, a partner in a private detective agency.

Hames said: "These events left me distressed, anxious and needing counselling and contributed to the breakdown of my marriage."

Leveson told her she did not have to continue.

But having recovered her composure, Hames, a former detective herself who said she had loved her job, told the inquiry: "No one from any walk of life should have to put up with it. I would hate to think of anyone having to go through what we have had 10 years of."

She alleged that former NoW executive Alex Marunchak colluded with suspects who ran the NoW's private detective operations. They put the family under surveillance and targeted their phones for hacking. Brooks, as editor, failed to act when confronted with the evidence in 2003, Hames said, and Marunchak was even subsequently promoted.

After the broadcast, Cook got official intelligence that the suspects planned "to make life difficult for him", and the programme was sent an email suggesting Hames was having an affair with a senior detective. Two vans stationed outside their house were eventually traced back to the News of the World.

Police at Scotland Yard did little to protect the couple. Instead, the head of PR at the Met, Dick Fedorcio, spoke to Brooks, who made the "absolutely pathetic" claim that the tabloid had targeted couple because of the alleged affair. "We had by then been married for four years, had been together for 11 years and had two children," Hames said.

In a meeting with her husband, she said Brooks "repeated the unconvincing explanation that the News of the World believed we were having an affair". Hames said: "I believe that the real reason for the NoW placing us under surveillance was that suspects in the Daniel Morgan murder inquiry were using their association with a powerful and well-resourced newspaper to try to intimidate us and so attempt to subvert the investigation."

She told the inquiry that it was impossible not to conclude that there had been "collusion between people at the News of the World and people who were suspected of killing Daniel Morgan".

Private investigator Jonathan Rees, said to have earned £150,000 a year from the News of the World for supplying illegally obtained information, was eventually accused of Morgan's murder but the trial collapsed and he was cleared last March.

• To contact the MediaGuardian news desk email editor@mediatheguardian.com or phone 020 3353 3857. For all other inquiries please call the main Guardian switchboard on 020 3353 2000. If you are writing a comment for publication, please mark clearly "for publication".

• To get the latest media news to your desktop or mobile, follow MediaGuardian on Twitter and Facebook.