Sir Cliff Richard felt "violated and betrayed" by BBC coverage of a police search of his flat, TV and radio presenter Gloria Hunniford has said.
In a witness statement presented to the singer's High Court privacy case against the corporation, she said her friend was left "extremely distressed".
Sir Cliff was not charged after South Yorkshire Police's investigation into a historical sexual assault claim.
The BBC says its August 2014 report was of legitimate public interest.
Lawyers for the broadcaster maintain it acted in good faith and its journalists had respected Sir Cliff's "presumption of innocence".
Ms Hunniford, who attended some of the court hearings with Sir Cliff, said she had been watching television when the BBC first reported officers were searching his home in Sunningdale, Berkshire.
"That the police were searching my friend's apartment was of course a shock in itself, but to witness the search being carried out on television apparently in real time, with a helicopter filming overhead, together with details of the appalling criminal allegations that the police were said to be investigating, seemed beyond belief," she said.
Sir Cliff, 77, is suing the BBC for the misuse of private information and breaking data protection rules.
He told the judge how the BBC decision to name him and report on the raid left him feeling "forever tainted" and "smeared".
Ms Hunniford's statement said Sir Cliff had always been the "most positive and upbeat of people" but after the coverage "he seemed a different person; broken and extremely confused".
She said there was a "real emotional and mental change... and even a physical one" in the two years it took for prosecutors to announce Sir Cliff would not be charged.
Ms Hunniford, who hosted a daily show on BBC Radio 2 for 10 years and currently presents Rip Off Britain on BBC One, has known Sir Cliff since 1969.
She said after the raid he "tried to keep things as normal as he could" and they continued to go on holidays together and spent occasional time at his home in Portugal.
"He was clearly trying to stay positive and put on a brave face on things, but he was not quite succeeding," she said.
Ms Hunniford said Sir Cliff later spoke of how relieved he was when cleared.
She added: "I could tell that he was, but at the same time I could still see evidence of the toll that this extraordinarily difficult time had taken upon him. When I gave him a hug, he had lost so much weight that he felt like skin and bones."
Ms Hunniford said while Sir Cliff now "seems more his old self and is looking a lot better... he cannot stop talking about how violated and betrayed he feels about the BBC decision to broadcast the police search of his apartment and create the media storm that ensued".
One of the singer's lawyers, Paul Morris, gave evidence to the court and described South Yorkshire Police's investigation into Sir Cliff as "astonishingly long".
Sir Cliff's business manager, Malcolm Smith, told the judge, Mr Justice Mann, it was hoped the investigation would be over within 12 weeks. But he said it was delayed by further false allegations that "would not have been made but for the BBC publicising the raid in the way they did".
'Bonkers but brilliant'
Police had been looking into a claim Sir Cliff sexually assaulted a boy under the age of 16 in Sheffield in 1985.
South Yorkshire Police has settled its own privacy case with Sir Cliff for £400,000 and argues that the BBC should pay a share of this because its actions were "far more causative of the damage suffered".
Former Det Supt Matthew Fenwick told the court on Monday that police only agreed to tell the BBC about the raid because it had wanted to stop reporter Dan Johnson breaking the story before it had a chance to search Sir Cliff's flat.
Details of text message conversations between Mr Johnson and South Yorkshire Police's head of media, Carrie Goodwin, on the day of the raid were raised in court by the BBC's barrister Gavin Millar.
The lawyer referred to a message Ms Goodwin sent a few hours after the search and the first BBC broadcast, to ask Mr Johnson whether he had had a "good day".
Mr Johnson said it had been "bonkers but brilliant. Thanks for your help. Hope it went well from your point of view. Any idea what happens next?"
In response, Ms Goodwin said: "Just waiting for meeting to be arranged - everyone thinks we tipped you off so lots of grief from the media but nothing we cannot handle."
Cross-examined by Mr Millar, she denied police had been "perfectly happy to use Johnson and the BBC after his initial approach to get coverage" for its "high profile" investigation, saying his suggestion "couldn't be further from the truth".
Ms Goodwin also rejected the lawyer's assertion the force had gone "out of its way" to help the BBC to report the case.