Image caption Gervais plays the title role in Derek, which has its premiere this week

Ricky Gervais has defended his new Channel 4 programme, Derek, following suggestions he was mocking people with learning difficulties.

The one-off comedy is billed as the story of "a simple, vulnerable man working in an old people's home".

Some, including fellow comedian Stewart Lee , have said the character makes light of the "mentally handicapped".

But Gervais, who plays the title role, said Derek was not intended to have a "specific and defined disablity".

"Derek is a fictional character and is defined by his creator, me," he told disability rights campaigner Nicky Clark .

"If I say I don't mean him to be disabled then that's it. A fictional doctor can't come along and prove me wrong."

Image caption Life's Too Short, about a dwarf acting agency, was also a target for criticism

"He's different. But then so are a lot of people. He's not the smartest tool in the box but he's cleverer than Father Dougal [from Father Ted], and not as different as Mr Bean.

"He's based on those people you meet who are on the margins of society. Nerds, loners, under achievers."

Gervais was interviewed for Clark's website ahead of the first screening of Derek on 12 April.

The campaigner has previously been a vocal critic of the comedian. Last October, she took him to task for repeatedly used the word "mong" on his Twitter feed.

She called on the 50-year-old to stop using the term, which can be used offensively in reference to people with Down's Syndrome.

"If you find abuse of disabled people sickening, then please don't use the terminology of bullies and thugs," she wrote in The Guardian .

The pair eventually made contact, and Gervais asked Clark to watch a pilot episode of Derek.

'Compassion'

She agreed with his assertions about the story, saying: "I've laughed and cried. I haven't seen cruelty."

"Instead of it being a mocking disintegration of a learning-disabled man -paraded for the amusement of comfortable unaffected people, it's the story that really needs to be told at the moment," she wrote on her website.

The character of Derek Noakes first appeared in 2001 as part of the Edinburgh show Rubberneckers, several years before the comedian achieved mainstream success with The Office.

Stewart Lee made his comments about the character last year, when Gervais announced the Channel 4 programme, and linked to old YouTube footage of Derek.

After watching the sketches, Lee said he "imagined feral children trailing real Dereks around supermarkets, chanting 'Derek Derek', as they doubtless would were the series to be made, and wondered if, sometimes, discretion is not the better part of valour".

But Gervais defended the character to Clark, saying it was meant to be sympathetic.

"It's important to have compassion for the characters you are portraying because at some level comedy and drama relies on empathy." he said.