The 81-year-old premier's final years in power were marked by slowing economic growth as his government struggled to overcome charges of weak leadership and corruption.

After making a final televised address to the nation in the morning, India's third-longest serving PM was driven to the presidency building in central New Delhi, where he tendered his resignation to President Pranab Mukherjee.

"Today India is a far stronger country than it was a decade ago," he said in a short and typically low-key speech, wearing his trademark blue turban. "I give you credit for it. We still need to work hard to take this country forward."

The economist also sent his best wishes to his successor Modi, a polarising Hindu nationalist whom Singh said in January would be "disastrous" for the country, in unusually forthright remarks.

"I am confident that India will emerge as a strong economy in the world, blending tradition with modernity and unity with diversity," Singh added.

The former finance minister, celebrated for pushing through pro-market reforms in the 1990s, will continue as a caretaker prime minister until 63-year-old Modi takes office some time next week.

Singh believes historians will be kinder to him than contemporary critics who have savaged his recent performance in office, overshadowed by corruption scandals and policy paralysis.

Amid sniping from cabinet colleagues about his weak communication skills, Singh's reputation took a further blow this month from an unflattering new book by a former aide titled "The Accidental Prime Minister."

It portrayed him as timid and controlled by Sonia Gandhi, the president of the Congress party, who handpicked him in 2004 after the first of two back-to-back victories.

"I owe everything to this country, this great land of ours where I, an underprivileged child of Partition, was empowered enough to rise and occupy high office," he said in his address.

"It is both a debt that I will never be able to repay and a decoration that I will always wear with pride."

Figures from the Election Commission showed the BJP had secured 280 seats and was projected to win another two in the 543-member parliament, the first majority by a single party since 1984.

The Congress party, India's national secular force that has ruled for all but 13 years since independence, was left obliterated, poised to win just 44 seats – a quarter of its tally in 2009