A human rights group is planning to stage a protest at the premiere of new movie The No 1 Ladies' Detective Agency.

The 90-minute pilot is based on Alexander McCall Smith's bestselling novels about the adventures of detective Precious Ramotswe in Botswana.

The Survival organisation has criticised the author's depiction of the African country, saying: "The books portrays Botswana in a rosy light, but the reality for bushmen is different.

"Their experience is one of bullying and persecution."

The film, directed by Anthony Minghella from a script he co-wrote with Richard Curtis, premieres at London's BFI on Friday.

The joint BBC and HBO production will be broadcast on BBC One over Easter.

Minghella and Curtis have been given the go-ahead to make a 13-part series based on the books.