India's main opposition alliance split on Sunday, with the second-biggest party in the coalition pulling out after Narendra Modi was elected to lead the dominant party's 2014 election campaign.

The Janata Dal United (JDU) ended ties with the National Democratic Alliance -- a federal coalition led by the Bharatiya Janata Party (BJP) -- saying it fears Modi's image could alienate voters in next year's polls.

"We have decided to end the 17-year-old political alliance. It is important to walk away when there is a difference of opinion and political thought," Nitish Kumar, a senior JDU leader and chief minister of eastern Bihar state told reporters.

Modi, the chief minister of Gujarat state known popularly as "NaMo", was earlier this month named election committee chairman for the BJP ahead of polls scheduled for the first half of 2014.

Despite the split BJP leaders said Modi would still lead their election campaign in 2014.

"We made every effort to keep the alliance intact but the JDU seems to have its own political agenda," said senior BJP leader Sushil Modi, who is not related to Narendra Modi.

"The fact is that Narendra Modi is here to stay and political parties are scared of his rise," he added.