Stone Roses frontman Ian Brown has told a court that former TV weatherman Fred Talbot tried to sexually abuse his friend on a school trip to Scotland.
He said Mr Talbot had been his biology teacher in Manchester, and would organise trips for pupils.
Mr Brown told Lanark Sheriff Court of an incident on a camping trip somewhere in Scotland in late 1977 or early 1978.
Mr Talbot, 67, of Greater Manchester, denies assaulting several boys on school trips between 1978 and 1981.
The singer told the court that one of his school friends told him that Mr Talbot attempted to abuse him after inviting him into his tent.
Mr Brown, who told the court he was self-employed as a singer and songwriter, said he had got on with Mr Talbot before the camping trip.
He said: “He was possibly one of the only teachers who didn’t stick (cane) me.”
The witness said Mr Talbot would regularly talk about trips during class but would only invite certain people.
“Mr Talbot did these trips and he decided who went,” Mr Brown told the court.
“You couldn’t just put your name down and say you were going.”
The witness said he did not know exactly where they had camped on his trip, but between 12 and 20 pupils had left school on a Friday afternoon in a minibus with Mr Talbot.
When they arrived the area was covered in snow and they cooked dinner.
Mr Brown said Mr Talbot had told them he was going to take someone to the pub and one of his friends was selected because he looked older.
He said that when they returned the friend was invited into Mr Talbot’s tent.
Asked what happened next by prosecutor Imran Bashir, Mr Brown said the boy had come back into the tent “in a state”, and had claimed that the defendant had tried to perform a sex act on him.
Mr Brown said: “I’ve never forgotten it, I was shocked.”
Questioned by defence lawyer Alan Gravelle, Mr Brown said he left school before Mr Talbot began to appear on TV but was aware of his career because “he was on the TV every night”.
Asked why he had not raised the incident with authorities previously, the singer said: “Every time I saw him on TV I told people this story.
“I’ve told hundreds of people the same as I’m telling you here.”
Mr Gravelle then asked if the witness had ever tried to tell Mr Talbot’s TV bosses when he appeared on music shows with the Stone Roses.
However, Mr Brown said it was “not realistic” to think he would break off from performing with his band to speak to someone.
Mr Talbot faces eight charges of indecent assault between January 1978 and November 1981, as well as one charge of lewd, indecent and libidinous behaviour in February 1978.
Six of the incidents are alleged to have happened on camping excursions in Moffat in Dumfries and Galloway, and three on boating trips on the Caledonian Canal in Inverness.
Mr Talbot, best known for presenting the weather forecast on a floating map in Liverpool’s Albert Dock for ITV’s This Morning programme, denies all the charges against him.
The trial continues.