Rajiv Gandhi was assassinated while campaigning in 1991

But Delhi's High Court ruled that the three billionaire Hinduja brothers should be tried for conspiracy to cheat the government, a charge they deny.

Prosecutors say Swedish firm AB Bofors paid them illegally in the $1.3bn sale of 400 howitzers to India in 1986.

The Bofors scandal was a key issue in Gandhi's 1989 election defeat. He was assassinated while campaigning in 1991.

After 17 years of abuse and vilification, it's a special moment today for me and my children, Rahul and Priyanka Sonia Gandhi

High Court judge JD Kapoor said there was no evidence of involvement in the deal by Gandhi or the late former defence secretary SK Bhatnagar.

"Sixteen long years of investigation by the [Central Bureau of Investigation] could not unearth evidence against them for accepting bribes", he said.

Gandhi's widow, Sonia, who is now the leader of the main opposition Congress party, was delighted with the verdict.

"My husband always said that one day his innocence would be proved. I hope the people who caused him so much pain will now rethink the falsehoods they spread about him."

Trial date set

Britons Srichand and Gopichand Hinduja and Swiss citizen Prakash Hinduja deny any wrongdoing.

The brothers head a global business empire in a number of sectors including banking, transportation and pharmaceuticals.

The judge cleared the Hindujas of conspiring with Gandhi and other public servants to cheat the Indian Government.

But they will face trial for entering into a criminal conspiracy to cheat the government.

The Hindujas were cleared of conspiring with the government

Prosecutors say they received millions of dollars in commission from Bofors, now known as Kartongen Kemi Och Forvaltning AB, for the deal.

Commissions on defence deals are illegal in India.

Ram Jethmalani, who has defended the Hindujas, has said the money paid by Bofors was part of a long-time consultancy agreement.

He told the Times of India the brothers "played no part whatsoever in the securing of the gun contract by Bofors".

The brothers had challenged a lower court's trial order in 2002 on the grounds that there was no material record to prove their involvement.

The judge said a magistrate was empowered to hear the cheating and conspiracy charges and set a trial date of 23 February.

The BBC's Ayanjit Sen in Delhi says the Bofors case has dogged India's political scene for over a decade and a half.

Indian prosecutors have over the years also charged Bofors agent WN Chadha, the Italian businessman Ottavio Quattrocchi and former Bofors chief Martin Ardbo.