The format of the BBC's new project, Tweenies, is a closely-guarded secret, but it is believed the series will feature four clearly defined characters - Jake, Fizz, Milo and Bella - with whom three to five-year-olds can identify.

The new characters are thought to resemble real children more closely than the brightly-coloured Teletubbies, who quickly became a cult favourite for children of all ages.

The Tweenies, who will make their debut in the New Year, will also be helped along in their adventures by two adults.

The BBC said the characters were similar to children in that they "play, learn, and explore the world around them".

260 episodes commissioned

A total of 260 episodes have been commissioned by the BBC from independent producer Tell-Tale Productions.

The corporation hopes the Tweenies will take off in the same way as the Teletubbies, which has proved to be a money-spinner for the BBC and independent producer Ragdoll Productions.

Overseas sales and merchandising made £23m last year.

However, the advent of the Tweenies will not mean the end for the Teletubbies.