Andrew Lloyd Webber has launched his new musical about the establishment’s “scapegoating” of a major figure in the Profumo affair – with the help of former showgirl Mandy Rice-Davies.

Rice-Davies and Christine Keeler were key figures in the 1963 sex scandal, which threatened to topple the Conservative government of the time.

The new musical, Stephen Ward, is the story of the society figure who is said to have introduced John Profumo, who later resigned as secretary of state for war, and showgirl Keeler at a party at Cliveden.

Ward, a London osteopath, was charged with living off immoral earnings. He took an overdose of sleeping tablets on the last day of his trial and was found guilty while in a coma.

Webber said that the musical was the story of how the “establishment used Stephen Ward to get off the hook” and how it “came together to find a scapegoat”.

He added: “We do pass judgement. We do make it very clear that he was very shabbily treated. There are people who feel it was one of the greatest miscarriages of justice that ever happened.”

Rice-Davies said she thought she would enjoy the show, which opens at the Aldwych Theatre in December, and that she agreed to take part, advising Webber, because she thought he would create an “honest witness”.

“I wanted the story told about Stephen Ward,” she said, “one that will fill the gap between the man and the myth”.

Rice-Davies said she had not seen the 1989 film Scandal about the Profumo affair. Asked if she worried about how she might be perceived, she said: “I’m 70 next year. Who gives a damn?”

She said that her former friend Keeler was not involved in the musical: “I haven’t seen Christine since the 1980s. Andrew wrote to her saying ‘would she like to be involved?’ But she had something of her own going on, she just wasn’t interested.” Rice-Davies added: “For some reason she doesn’t like me. I can’t understand it. Maybe it’s because I lived abroad, I escaped the obvious prejudice she’s suffered.”

She said of Ward: “Stephen Ward was difficult, an oddball. He was certainly part of the vanguard movement of free love and free sex and being at the vanguard, he got shot down first. Of course, he was a scapegoat. The government was trying to control public morals.”