Jerry Hicks was sacked from his job last month

He attended a 400-strong rally on Wednesday for Jerry Hicks, the Amicus convenor dismissed from his post after allegations of misconduct.

Mr Benn told the BBC: "It is a direct attack on the rights of working people who organise themselves."

A hearing is due to take place in the next six months into the dismissal.

Tony Benn's message to the rally was: "Back Jerry Hicks and the union. They are right. The company is wrong.

"I have known Rolls-Royce for 55 years. I think it is disgraceful.

"It is, in the end, a human question. Here is a guy who has worked for the company for years and years."

Amicus is demanding Mr Hicks' reinstatement with Rolls-Royce, and about 100 engineering workers at the Filton plant are to strike in support of him next Monday.

Mr Hicks said his fight for reinstatement at the Patchway plant would continue for "as long as it takes".

Rolls Royce has declined to comment.