* Sonia Gandhi takes centre stage with appeal to avert Congress election defeat
* Address makes no mention of opposition candidate Narendra Modi, but clearly aimed at him
* Opposition BJP dismisses appearance as "farewell speech"
By Douglas Busvine
NEW DELHI, April 15 (Reuters) - Sonia Gandhi, president of India's ruling Congress party, has issued a rare direct appeal to the nation not to return an opposition she said was motivated by "hatred and falsehood" in the country's general election.
The three-minute TV address was aired at prime time on Hindi-language channels just as an opinion poll showed for the first time that an alliance led by the Hindu nationalist Bharatiya Janata Party (BJP) could win an outright majority.
"Their vision, clouded with hatred and falsehood, their ideology, divisive and autocratic, will drive us to ... ruination," the Italian-born widow of 1980s prime minister Rajiv Gandhi said in the clip broadcast on Monday night.
Gandhi, 67, has taken centre stage in a bid to avert what polls predict will be the worst-ever election defeat for Congress, after a weak campaign led by her son and political heir apparent, Rahul.
The BJP dismissed the address as "a farewell speech given in desperation", driving home an advantage it has reaped from recent accounts by former government insiders that Sonia Gandhi had kept Prime Minister Manmohan Singh on a tight leash.
"She wants to give power to the people but did not give power to the prime minister," Prakash Javadekar, the BJP's national spokesman, told Reuters.
HEART AND SOUL
Sitting in a book-lined study and wearing a dark red Sari, Sonia Gandhi did not mention the BJP's prime ministerial candidate, Narendra Modi, by name.
But her comments clearly targeted his brand of Hindu nationalism that she believes poses a threat to social peace in India's diverse society of 1.2 billion, and at a BJP campaign focused on Modi that critics say smacks of a personality cult.
"It is this, the very heart and soul of India, that we are fighting to protect in this election, from those who seek to change it, and to divide us," said Gandhi. "They want to impose uniformity. They say: 'Just believe in me.'"
Modi, 63, is campaigning as a no-nonsense administrator who has fought corruption and nurtured investment during more than a decade as chief minister of the western state of Gujarat.
But questions persist over an eruption of sectarian bloodshed in Gujarat in 2002 in which more than 1,000 were killed, mostly Muslims. Modi has denied accusations that he failed to halt the riots, and a Supreme Court inquiry found that he had no case to answer.
A senior Modi aide has, however, been banned from campaigning by the election authorities for statements directed at minority Muslims in Uttar Pradesh that promoted "hatred and ill-will". The northern state, India's most populous, is a must-win territory for any party staking a claim on power.
India's five-week general election, which kicked off on April 7, has seen a high turnout so far in what some analysts say is evidence of a "Modi wave" that could propel the BJP to power for the first time in a decade.
The latest opinion poll, for private news channel NDTV, showed the BJP and its allies winning 275 parliamentary seats, enough for a three-seat majority. That was an increase of 16 seats from the last NDTV poll just over a week ago.
The biggest round of voting comes on Thursday, with 122 seats being contested in regions in the north, including Uttar Pradesh, Karnataka in the south and Rajasthan in the northwest. Voting ends on May 12, with results due on May 16. (Additional reporting by Manoj Kumar; Writing by Douglas Busvine; Editing by John Chalmers and Ron Popeski)