Celebrities who avoid milk in favour of trendy vegan diets are hampering the dairy industry, farmers say.

They fear that stars like Gwyneth Paltrow, Victoria Beckham and Megan Fox are putting the public off dairy in greater numbers than ever by aggressively promoting vegan diets.

Colin Evans, chairman of the Welsh Dairy Show, told the BBC: 'Celebrities are now getting behind promotional drives for veganism or vegetarianism.

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Influencers: Gwyneth Paltrow recommended ditching dairy as part of a detox last year, while Victoria Beckham, right, is said to have treated bad skin that way

'We must have the answers ready for these people and to prove that we do look after our animals and we do produce food in a healthy manner.'

Gareth Richards, a National Farmers' Union board member, added: 'The vegan activism we've seen in recent months represents an extremist view of dairy farming which portrays a completely inaccurate image of the UK dairy industry.'

Miss Paltrow recommended ditching dairy as part of a detox last year, while Miss Beckham is said to have treated bad skin that way. Actress Miss Fox has also credited her slim figure to going dairy-free.

Beauty sectet? Actress Megan Fox has also credited her slim figure to going dairy-free

Dairy is an important source of calcium, however the health benefits are not getting through to younger generations, it is claimed. David Dobbin, head of United Dairy Farmers, said last year: 'It's a demographic time bomb. We are facing a fall-off in demand for dairy.'

One in five households now buy non-dairy products such as soya, oat or almond milk.

The size of the non-dairy market leapt from 36 million litres in 2011 to 92 million litres in 2013, a 155 per cent increase.

Meanwhile, sales of milk and cream grew at a sluggish 3 per cent over the same period.