India’s richest brothers will go head-to-head in the country’s highest court today to fight out a $17 billion (£10 billion) dispute over the sub-continent’s largest gas find.

Mukesh and Anil Ambani have become infamous for their mutual animosity. Such is their wealth and influence — between them, the multibillionaire brothers account for more than 5 per cent of India’s annual GDP — that some fear their feuding poses a threat to the country’s prosperity.

The Supreme Court hearing in Delhi also promises to expose the Indian Government’s ad hoc approach to energy security — a factor, some believe, in the reluctance of overseas groups to bid for exploration rights — and a number of cosy relationships between state officials and one of India’s wealthiest families.

The brothers, who are not expected to appear in court, fell out after the death in 2002 of their father Dhirubhai Ambani, who rose from rags to riches by creating Reliance, an empire that ran from petrochemicals to telecoms. Despite his success in business, however, he left no will.

In 2005 the group was split between the feuding siblings under terms hammered out by their mother Kokilaben, the only person able to mediate between them.

Since then, the pair’s dealings have deteriorated sharply, resulting in a series of tit-for-tat legal actions and verbal assaults.

Last year, the elder Mukesh, 52, looked to block a potential £35 billion deal that would have allowed Anil, 50, to create a new colossus in the global mobile phone industry.

Months later, a furious Anil sued Mukesh for more than $1 billion for alleged defamation in an American newspaper.

Their biggest row by far, however, has been over vast gas deposits discovered in 1999 off India’s east coast after the then unified Reliance snapped up the exploration rights to the D6 block of the Krishna-Godavari Basin.

Under the corporate split terms brokered by their mother, Mukesh’s Reliance Industries agreed to supply gas to Anil’s Reliance Natural Resources at a fixed price of $2.34 per million British thermal units (MBtus) for 17 years.

In 2006, Mukesh claimed that the deal needed the approval of the Indian Government, which subsequently set a higher price of $4.20 per MBtu, setting an epic legal battle in motion.

Anil’s camp is arguing that the fear of further government intervention has deterred foreign companies from bidding for exploration rights in India. It also claims that the Indian public’s fuel bills could rise if Mukesh wins and that the older brother has been improperly favoured by the Ministry of Petroleum, which is headed by an old family friend.

Mukesh’s people say that the original deal was always subject to government approval and that the higher price is legally sound. They also believe that the commercial landscape changed dramatically when oil prices spiked after the original price was formulated.

The stakes are very high: Mukesh is expecting to make $11.5 billion from the gas if he is allowed to sell it at $4.20. If Anil wins the court case, that may tumble to a $5.4 billion loss.

Analysts also say that the future of Anil’s company, presently valued at nearly £2 billion, hangs in the balance. The gas supply contract, Anil told shareholders in July, is “our company’s primary asset and contributes most of its value”.

So far, Anil has come closest to extending an olive branch. This month, after making a pilgrimage to two holy shrines in the Himalaya. “seeking divine inspiration and blessings”, he published a statement saying that he and his brother could negotiate a settlement.

In response, people close to Mukesh say that he, too, is quite willing to sit down and talk — just as soon as Anil admits that he is in the wrong.

Times Recommends

• Minister in talks with Saudis to protect creditors
• Premier Inn hits back in £29-a-room row
• Bankers hit back at 'populist' bonus supertax