Some came from their hospital beds, others from their prison cells, as Indian MPs gathered today for a no confidence vote that will decide the fate of the coalition government and its historic nuclear deal with the United States.

The vote, expected at around 6pm (1230 GMT), will conclude a passionate two-day debate in parliament and a frantic fortnight of backroom bartering as the government and the opposition battle to make up the numbers.

Pollsters put the government a whisker ahead this morning, with just less than a majority in the 543-seat parliament, but the numbers were still in flux amid multiple defections and allegations that votes are being bought for three million pounds apiece.

So close is the race, and so high the stakes that the opposition has even flown in one MP who had open heart surgery in Bombay last week, and another who had been recovering from knee surgery in Los Angeles.

The government, meanwhile, has temporarily released six MPs who are in jail for crimes including murder and extortion, hoping that at least five of them will support it.

"We will prove our majority on the floor of the house," vowed Manmohan Singh, the Indian Prime Minister, before tabling the confidence motion yesterday.

If the Congress Party and its allies in the ruling coalition lose, the government will collapse, triggering a snap election as soon as November that could bring the Hindu nationalist Bharatiya Janata Party (BJP) back to power..

If the government wins, it will proceed with the nuclear pact, allowing India to import US nuclear fuel and technology and cementing a new strategic friendship with Washington, its old Cold War rival.

It will also wait until early next year before calling the election, which must happen before May.

Mr Singh, who brokered the nuclear deal with President Bush in 2005, appeared confident as he arrived at parliament for the vote this morning, making a “V” for victory sign for the second day running.

Sonia Gandhi, the Italian-born Congress Party leader, and her son and heir apparent, Rahul, are both expected to address parliament this afternoon.

They say the deal will help to ease India’s chronic energy shortage, which it estimates will reach 145 gigawatts - or roughly double Britain’s current generating capacity – by 2030.

Times Recommends

• Would you live on the wrong side of the Berlin Wall?
• Wish you were here, says Iraq tourist board
• Russian policeman’s corruption plea to Putin