British energy firm BG Group Plc said on Thursday it wants to double its investment in India to $1.0 billion in the next five years as demand for gas is booming in line with an expanding economy.

"The reason we think we could twofold our investment (in India) is the fast growing demand for energy and particularly for gas," David McManus, BG's executive vice president told Reuters in an interview at a roadshow promoting Indian oil and gas.

"So far we have spent $500 million and we are pleased to think there is potential to double investment in the next five years," he said.

Demand for gas, fuelled by a growing middle class of about 30 crore (300 million), is 130 million cubic metres (4.6 billion cu ft) per day while production in the nation of 100 crore (1 billion) people is only half that.

Environmental concerns fuelling a move from oil to less polluting gas will also help underpin demand.

He said BG, which is focusing on India, whose GDP growth is averaging six per cent, were investing in two areas: distribution and the exploration and production sector. "We want to double production at our fields within four years and potentially put in another $750 million of investment (in them) of which we would pay 30 per cent," he said.

Last year BG acquired 30 per cent in the Tapti and Panna Mukta gas fields in northwestern India and McManus said output from Tapti could easily rise to 450 million cubic feet (12.74 million cu metres) from 185 million.

In distribution BG wants to boost its client base of 250,000 in Maharashtra as well as expand the number of 150,000 customers it has in Gujarat.

He declined to give any targets for how many more customers the company plans to snarl and that BG wants to bring in gas from Iran which has one of the biggest reserves in the world, drawing on a good relationship between the two countries.

In March BG's chief executive Frank Chapman told Reuters in an interview it had taken the first steps towards building a liquefied natural gas plant in Iran in what would be a joint venture with the National Iranian Oil Company.

McManus reiterated Chapman's hopes to reach a final agreement before the end of the year for the construction of the plant, which was likely to be built in Tombak on the southern Iranian coast.

"We are on track and we still think we could reach an agreement this year," he said.

Gas is most often delivered by pipeline but LNG -- gas cooled or pressurised into liquid form for shipping -- allows producers to exploit more remote gas fields and move gas from one continent to another.

BG, already an LNG producer in Trinidad and Tobago, started building an LNG export facility in Idku near Alexandria in Egypt in 2002, with first deliveries planned in 2005.

It also plans to build an LNG terminal at Brindisi in Italy, which it says could be ready in 2006.