The organisers of an Indian film festival said Friday the government had pressured them to drop a documentary on the beef industry, amid a heated debate about beef eating in the majority-Hindu country.

Officially secular India is the world's biggest exporter of beef, but the slaughter of cows -- which Hindus consider holy -- has long been contentious.

Organisers said the documentary, called "Caste on the Menu Card", was the sole film of 35 submitted to the Information and Broadcasting ministry they did not clear, ahead of the Friday opening of the Jeevika: Asia Livelihood Documentary Festival in New Delhi.

"They told us verbally to drop it as it's a controversial issue. The other 34 documentaries were granted certificates," said Avinash Chandra, one of the annual festival's organisers.

"When we asked them to provide a reason for not granting permission they said the documentary is on a contentious topic."

The beef issue has become particularly divisive in recent months, with one Muslim man lynched over false rumours that he had killed a calf for food.

Chandra said there was "nothing controversial" about the film, which looked at the beef industry in the western city of Mumbai -- home to a large Muslim community.

Mumbai is the capital of Maharashtra state, which recently toughened its laws on beef, in a move that hit the city's mainly Muslim-run slaughterhouses hard.

A ministry official contacted by AFP refused to comment on the move.

Most Indian states already ban the slaughter of cows, although many allow the killing of buffaloes -- whose meat Indians also call beef.

Indian Prime Minister Narendra Modi's Hindu nationalist government has made no secret of its desire for a nationwide ban on beef.

But that would be unpopular with many Muslims and Christians as well as some lower-caste Hindus, for whom it is a relatively cheap source of protein.

The issue has become hugely divisive in india.

This week the editor of the government magazine in the northern state of Haryana was reportedly fired for publishing an article on the health benefits of beef.

And in New Delhi, police were called to investigate a canteen run by the state government of Kerala after a member of a Hindu group complained that it served beef.

The meat turned out to be buffalo, which is legal in the Indian capital.

Critics say that Hindu extremists have been emboldened by Modi's failure to speak out against violent incidents such as the murder last month of Mohammad Akhlaq, who was beaten to death last month over unsubstantiated rumours he had eaten beef.