The legendary French movie star turned animal rights campaigner Brigitte Bardot has written to Nepal's president urging him to stop a mass animal sacrifice from going ahead next week.

A temple in Nepal will host what is thought to be the world's biggest ritual slaughter in which hundreds of thousands of buffaloes, goats and birds will be sacrificed to the Hindu goddess of power, Gadhimai.

In a letter seen by AFP Friday, Bardot urged the president to outlaw the sacrifice of animals for religious purposes ahead of the festival, calling the practice "violent, cruel and inhumane."

"I personally find it hard to imagine that your heart can withstand such cruelty, knowing that you, being the head of the country, are ultimately responsible," said Bardot, 75, in her letter to President Ram Baran Yadav.

"I have dedicated my life to protect animals and the best gift I could receive for this life-long struggle would be the announcement of the stopping of ritual sacrifice of animals."

Nobody at the president's office could be reached for comment on the letter, but the government has already said it will not bow to activists' demands to stop the Gadhimai festival, held every five years in southern Nepal.

Authorities here say the mass sacrifice, which attracts Hindu devotees from across Nepal and from neighbouring India, is a centuries-old religious tradition that should be allowed to continue.

Bardot shot to international fame in 1956 with her controversial role as a demon-driven temptress in the movie "And God Created Woman," becoming an icon of the burgeoning sexual liberation era.

But stardom proved too much to handle and she abandoned her movie career in 1973, aged just 39, retiring to the French Riviera resort of Saint Tropez.

Since then she has swapped the role of sex symbol for that of campaigner, selling off everything she owned to fund her animal rights foundation.