NEW DELHI, April 11 (Reuters) - A former media adviser to India's prime minister has alleged in a new book that Manmohan Singh allowed his authority to be undermined by Sonia Gandhi, president of the Congress party and standard-bearer of the Nehru-Gandhi dynasty.
Sanjaya Baru's book, "The Accidental Prime Minister", was published on Friday, days after India began a five-week election that is expected to oust Singh's Congress-led coalition from power after two successive terms.
Singh's spokesman dismissed the book as an incorrect interpretation of the prime minister's 10 years in power.
But the memoirs, which show the prime minister as subservient to a woman without an official government position, are likely to hand the opposition Bharatiya Janata Party (BJP) a stick with which to beat the Congress party in an increasingly acrimonious campaign.
"You must understand one thing. I have come to terms with this," Baru recalled the prime minister telling him in 2009.
"There cannot be two centres of power. That creates confusion. I have to accept that the party president is the centre of power. The government is answerable to the party."
Singh's spokesman Pankaj Pachauri described the book as "an attempt to misuse a privileged position and access to high office to gain credibility".
"The commentary smacks of fiction and (the) coloured views of a former adviser," Pachauri told reporters.
Baru was not immediately available to comment.
His book portrays Singh, 81, as an admirable man who held every important position in economic policymaking - including as finance minister when India embraced radical reforms in 1991 - before he became prime minister in 2004.
Singh also made history, becoming India's first prime minister from a minority community - he is a Sikh - and serving for longer than anyone other than a Nehru-Gandhi.
"On the other hand, the public perception that he accomplished this feat through unquestioning submissiveness lies at the heart of the image problem that came to haunt Dr. Singh," Baru said in his book.
Baru described Singh as an enigmatic man of few words who confessed when he became prime minister that he was not prepared for the role and shied away from telling his own "powerful tale".
But he said Singh's failure to assert himself after the Congress party was re-elected in 2009 proved to be a fatal flaw that weakened his authority and left him "in office" with some authority but not "in power".
He said that Singh conceded most of his turf as prime minister to Sonia Gandhi and senior cabinet ministers.
"The politically fatal combination of responsibility without power and governance without authority meant that Dr. Singh was unable, even when he was aware, of checking corruption in his ministry without disturbing the political arrangement over which he nominally presided," Baru wrote. (Reporting by John Chalmers; Editing by Frank Jack Daniel)