Gorbachev is getting involved in a high-profile case

The plea came in an open letter published on Mr Gorbachev's website.

Russian prosecutors say Alexander Ponosov ran pirated software at school, violating intellectual property rights.

In reply to Mr Gorbachev, Microsoft said it did not launch the prosecution and that the scale of the case did not warrant criminal proceedings.

Mr Gorbachev's letter, on the website run by his charitable foundation, said "many people in Russia regard this scandalous case as trumped-up, launched on the initiative of Microsoft corporation to set a precedent".

"We have great respect for the work of Microsoft's programmers... and are in no way casting doubt on the principle of punishment for intellectual property violations.

"However, in this case we ask you to show mercy and withdraw your complaint against Alexander Ponosov," the letter read.

'Amicable settlement'

But Olga Dergunova, chairman of Microsoft Russia, said: "This case was initiated by Russian authorities under Russian law.

"We did have the option in this case to take up civil action, but decided last year not to do so."

She added: "We are eager to see this case resolved through an amicable settlement so that everyone can move forward."

Russian President Vladimir Putin has also criticised the prosecution of Mr Ponosov, in Perm, east of Moscow.

The Perm region lies in the Ural Mountains, between Moscow and Siberia.

The teacher is accused of knowingly using pirated Windows software in the school and causing the company losses put at 266,000 roubles ($10,000; £5,000).

Mr Ponosov told the BBC that Russian prosecutors had brought the case against him and he was unaware of any Microsoft claim against him.

He says he is innocent, that the software had been pre-installed and he did not know it was unlicensed when he obtained the computers.

At a news conference on 1 February, President Putin said investigators should "go after the distributors, not the users".

"It's ridiculous to just arrest a chap for using computers," he said.