Former French president Francois Hollande has fuelled controversy over India's multi-billion-dollar 2016 purchase of 36 Rafale fighter jets, saying that France was given no choice on the Indian partner for manufacturer Dassault.

His comments on Friday stoked debate over a subject which has gained significant traction in India in recent weeks, since the opposition Congress party accused Indian Prime Minister Narendra Modi of favouring a private conglomerate over a public company in the aircraft deal.

The party alleges Modi gave preferential treatment to industrialist Anil Ambani, the billionaire chairman of Reliance Group, to the detriment of state-run Hindustan Aeronautics Limited (HAL).

Officials in India and France say Dassault had freely chosen to partner with Reliance, despite Ambani having no previous experience in the aeronautics sector.

"We did not have a say in that," Hollande told investigative website Mediapart.

"It was the Indian government that proposed this service group (Reliance), and Dassault who negotiated with Ambani."

"We did not have a choice, we took the interlocutor who was given to us," added Hollande, who was president of France from 2012-2017.

French firm Dassault had spent years negotiating a deal for 126 fighter jets to be manufactured in India with HAL, but talks had stalled.

On taking office, the Modi government cancelled the negotiations and decided to directly purchase 36 jets made in France.

Hollande denied any conflict of interest with Reliance, which partially financed a film produced by his girlfriend Julie Gayet in 2016.

"That is why, moreover, this group (Reliance) did not have to give me any thanks for anything. I could not even imagine that there was any connection to a film by Julie Gayet."

Speaking to AFP on the sidelines of a meeting in Canada on Friday, the former French leader insisted that France "did not choose Reliance in any way".

When asked whether India had put pressure on Reliance and Dassault to work together, Hollande said he was unaware and "only Dassault can comment on this".

'The PM has betrayed India'

Contacted by AFP, France's embassy in New Delhi did not comment.

India's defence ministry wrote on Twitter that neither the Indian nor French government "had any say in the commercial decision".

The French foreign ministry later issued a statement saying that "the sole obligations of the French government were to assure delivery and the quality of the equipment".

Paris was "in no way involved in the choice of Indian industrial partners," it added.

For its part, Dassault Aviation said in a statement on Friday that the contract was "a government-to-government agreement".

Congress President Rahul Gandhi, who has led the opposition's focus on the deal, wrote, "Thanks to Francois Hollande, we now know he (Modi) personally delivered a deal worth billions of dollars to a bankrupt Anil Ambani."

"The PM has betrayed India. He has dishonoured the blood of our soldiers," Gandhi added.

Foreign manufacturers obtaining arms contracts in India are obliged to reinvest a portion of the sums collected in India.

Under the Rafale deal, France must spend amounts totalling around half the eight billion euros ($9.4 bn) paid by the Indian government.

Dassault has invested more than 100 million euros in its joint venture with Reliance.

India — the world's largest defence importer — has been investing tens of billions in updating its Soviet-era military hardware to counter long-standing territorial disputes with its nuclear-armed neighbours, including a strengthening China.

It intends to use compensations payments such as in the Rafale deal to create a local defence industry.