A quiet lunch between European Union ambassadors and Indian prime ministerial contender Narendra Modi has shattered what remained of a decade-old informal boycott of the Hindu nationalist political leader.

The January 7 lunch at the German ambassador's residence in New Delhi will likely be seen as a major boost to Modi's quest for mainstream acceptance. The meeting went unpublicised until an Indian newspaper reported on it on Friday.

Modi, the charismatic chief minister of Gujarat, is praised by corporate India and foreign investors for presiding over an economic boom in his state.

But charges he was complicit in riots in Gujarat that killed at least 1,000 people, most of them Muslims, have cast a shadow over his ambitions. Critics accuse him of not having done enough to stop the violence, allegations he has strenuously denied and have never been proven.

After the riots, he was shunned by Western governments. Washington denied him a visa and EU ambassadors in Delhi cold-shouldered him. However, in recent years the EU's informal boycott had crumbled. Sweden and Denmark decided it was better to engage with him than ostracise him and Britain's ambassador met Modi in Gujarat last year.

Since being re-elected for a fourth successive term as chief minister in December, Modi has been on a seemingly unstoppable march towards becoming the Bharatiya Janata Party's (BJP) candidate for prime minister in elections due by May 2014.

EU ambassador Joao Cravinho told CNN-IBN television that Modi was a "major political figure" and it was therefore important to listen to his views. European and U.S. companies have made major investments in Gujarat.

Cravinho said the ambassadors had pressed Modi on the 2002 riots to find out "what went wrong, what should have happened, what the situation is now".

"We were pleased that he was able to tell us that because of a number of changes that he has introduced that such events could not be repeated in 2013," Cravinho said, without elaborating on what those changes were.

He did not respond to a Reuters request for comment, and the German embassy referred foreign media inquiries to Berlin.

If Modi is nominated as the BJP's candidate he could face Rahul Gandhi, heir to the Nehru-Gandhi dynasty, who is widely seen as the ruling Congress party's likeliest contender for the premiership if it and allies win a convincing majority.

Government minister Manish Tewari of the Congress party tweeted: "EU says accountability for Gujarat pogrom must be fixed. Does buck not stop with their lunch guest?"

Modi's challenge in projecting himself as a national leader was underscored this week when police were forced to use water cannon to disperse left-wing protesters at a New Delhi university where he was giving a speech.