Congress makes a clean sweep in the Election.

India's ruling Congress-led coalition was re-elected today for a second term with a stronger mandate, as voters nationwide gave an unexpectedly clear endorsement of prime minister Manmohan Singh's left-of-centre administration, setting the stage for an era of greater political stability.

The Congress party delivered its best performance for decades, and while it will still need the support of regional parties outside its United Progressive Alliance (UPA), it was expected to form a considerably more powerful government that it did in 2004, and one more able to push through an ambitious reforming programme.

Congress leader Sonia Gandhi stood with Singh outside her home in central Delhi to thank the electorate. "Eventually, the people of India know what is good for them," she said. "They always make the right choice."

Singh added: "I express my deep sense of gratitude to the people for the massive mandate they have given."

With many Congress supporters calling on her to appoint her son, Rahul Gandhi, 38, as prime minister, Sonia Gandhi made it clear that Singh, 76, would remain at the head of the government. However, Singh said he hoped to promote the heir to the Gandhi-Nehru dynasty to the cabinet and analysts described this election as a significant moment in Rahul's gradual but unwavering ascent to power.

Outside, a sea of supporters gathered to celebrate the victory, setting off fire-works, beating drums and waving posters of Sonia, Rahul, and his sister Priyanka, who was also an energetic campaigner during the run-up to the vote.

Once again proving Indian opinion polls are to be treated with great scepticism, Congress defied exit polls and analysts' predictions, which for days had predicted a much closer result, anticipating that regional parties would play a central role.

Instead, the results showed the reverse, with a clear resurgence of the Congress party as a national force. With more than 70% of the vote counted, the Congress-led UPA was set to take more than 258 seats, and the opposition alliance led by the Bharatiya Janata party forecast to take 162. Politicians such as the Dalit leader, Mayawati, chief minister of the northern state of Uttar Pradesh, had hoped to play an influential role in the formation of new government, but found themselves unexpectedly irrelevant in the face of the Congress party's strong showing.

Congress alone, without its allies, could take around 198 seats, according to the CNN-IBN news channel, far ahead of any other political party. While the UPA had not yet reached the 272 target necessary for a majority in the 543-member parliament, it was expected to make up that shortfall from regional allies without difficulty.

This means that when the next government is formed in the coming two or three days, the Congress leadership will not be obliged to give away key ministries to allied parties, but will be able to create a much more united government. The precise formation of such a government was unclear last night, as Sonia Gandhi and Singh discussed which parties to invite to join their coalition.

In a televised announcement, Arun Jaitley, a senior official from the BJP, conceded defeat, announcing that his party respected the people's mandate. He refused to speculate immediately on what might have caused the "disappointing" performance, commenting only: "Some things certainly did go wrong." The result is likely to signal an end to the career of LK Advani, the BJP's 81-year-old leader.

The left parties lost power nationwide, and the Communist Party of India (Marxist) leader, Prakash Karat, admitted his party "suffered a major setback".

Preliminary analysis of what motivated this stronger endorsement of the Congress party focused on the confident handling of the economy by prime minister Singh, whose supervision of India's finances has led to five years of strong growth. In recent months, India has been touched by the fallout from the global economic crisis, but the impact has been considerably less severe than elsewhere. Financial analysts expected the Indian stock market to rally when it opens on Monday.

As the results came out, Congress politicians described the surge in nationwide support as a vote for the party's pro-poor measures. Although the party has been criticised for the patchy implementation of its pro-rural poor initiatives, there is a recognition that the scale and ambition of programmes such as the national rural employment guarantee scheme (which promised 100 days of work at minimum wage salary for everyone) have begun to make inroads into the extreme poverty which remains in much of India's rural heartland.