NEW DELHI: Veteran Indian opposition leader Lal Krishna Advani resigned on Monday, a day after his party chose hardliner Narendra Modi to lead next year's election campaign, a source in his office told AFP.

Advani, the 85-year-old stalwart of the Bharatiya Janata Party (BJP) and a former deputy prime minister, resigned from all his positions within the party, the source said.

“He has submitted his resignation letter to the party chief,” the source said on condition of anonymity. The Press Trust of India reported that Advani, the BJP's prime ministerial candidate during the 2009 general elections, quit the party due to differences over its direction.

“Most BJP leaders are concerned just with their personal agendas,” the news agency quoted Advani's resignation letter as saying.

The comment is an apparent criticism of Modi, who was chosen by the Hindu nationalist party Sunday to head its campaign for national elections due by next May.

Advani did not attend the meeting of the BJP's national executive in an apparent protest over Modi's elevation, although the official reason given was illness.

Advani, who mentored Modi and defended him against criticism that he failed to stop deadly anti-Muslim riots in 2002, is now opposed to the 62-year-old's rise, according to media reports.

His resignation highlights the difficult road ahead for Modi, a hardline Hindu nationalist, who will need to win the backing of other senior BJP members as well as the party's regional coalition partners before he can lay claim to the prime ministerial candidacy.