A star of Dragons' Den, the hit television series about entrepreneurs, has become embroiled in a row over discrimination after declaring that fat people work less hard than colleagues who keep fit.

Duncan Bannatyne, one of the so-called 'Dragons' who grill nascent businesspeople seeking investment, said that all his experience in life and work had taught him that someone who neglects their health 'will just smoke cigarettes or stuff themselves with pies'.

Bannatyne told The Observer: 'Fat people don't work as hard as people who are not fat.'

Asked if this was directly related to their weight, the multimillionaire added: 'Obviously, yes. It's clear if people who are fat are not working as hard as people who are not fat, then it's to do with their weight. It's not my job to explain it; it's a fact.' Bannatyne, who grew up in poverty and now owns a health club chain, said he was referring to work where some physical exertion was involved. 'If someone came to me who was 20 stone, a cigarette hanging from their lip and carrying a beer bottle, would I be more inclined to employ that person or a person who's looked after themselves, goes to the gym, is fit and takes pride in their appearance? I think somebody who's fit can think faster and work faster. Somebody who hasn't looked after themselves won't train their brain, won't train their body, will just smoke cigarettes or stuff themselves with pies. They're less likely to go out and want to apply themselves and work hard.'

Bannatyne said he did not believe obesity campaigners would be upset by his remarks. But the charity The Obesity Awareness and Solutions Trust (Toast) was swift to condemn him. Siobhain Santry, a spokeswoman, said: 'It is appalling that someone in his position should make this remark. He falls into the trap of not being able to see the person, only the weight, and assuming a person with a weight problem is naturally lazy, greedy and has no self-respect. It's a stereotype, like a fat Andy Capp. He's out of touch with the causes of obesity and he's out of touch with having compassion for people.'

Santry added: 'Anyone with a weight problem has a self-esteem issue and they don't need someone like Duncan Bannatyne condemning them. It's just unhelpful. He is condemning the two-thirds of the adult population who are overweight or obese, which must include his own workforce. We see a lot of people in business whose weight goes up because they are so driven by work that they can't make time for themselves. As a respected business leader, Duncan Bannatyne should realise that we need more joined up thinking from the business community to be better employers.' Her criticism was echoed by the campaign group Fat is the New Black, which argues that discrimination against overweight people exists as racism once did. Its founder, Vicki Swinden, who weighs more than 20 stone, said: 'He's completely wrong. Because he was in the public eye, he will be unaware of the high number of busy, hard working and successful fat people there are. It's his loss.

'It's such a banal comment that he has gone down in my estimation. There is no scientific evidence to show that someone's brain works more slowly depending on their body size, or that if someone is more fat then they are less able. The perception is that fat people are thick, but they are not different from you or Duncan Bannatyne. They just look different.' She added: 'It's sad that he's proving himself to be of limited intelligence on this subject.'

Dragons' Den, presented by Evan Davis, will return to BBC2 later this year. The BBC declined to comment on whether it will speak to Bannatyne about his views on obese entrepreneurs.

Great Gaffes

'Some of our earrings are cheaper than a Marks & Spencer prawn sandwich, but probably won't last as long. We also do cut-glass sherry decanters complete with six glasses on a silver-plated tray that your butler can serve you drinks on, all for £4.95. People say: "How can you sell this for such a low price?" I say: "Because it's total crap." '
· Gerald Ratner in 1991

'Our customer is the everyday 18-year-old lad. Very few of our customers have to wear suits to work. They'll be for his first interview or first court case.'
· Top Man brand director David Shepherd explaining in 2001 that his target customers were football hooligans.

'People have realised it probably won't be you. You would be lucky to win a tenner.'
· Dianne Thompson, chief executive of Camelot, in 2002.