He told the StyleDNA podcast: “There’s almost no non-plastic in sportswear these days.

“I think what’s been really interesting, having launched it a couple of weeks ago, is that so many people have said ‘Ooh, I never thought about it as being plastic’.

“We’re very aware of plastic in lots of areas of our lives, but lots and lots of people are unaware that polyester, acrylic, nylon, polyamide – all of these things, vegan leather, is plastic.

“The really dreadful thing is because we throw so much of this stuff away, and because so much of it is really not very biodegradable at all – in fact some of the materials like elastane we don’t think have any mechanism of biodegrading – this stuff just never goes away.

“And a third of all the ocean microplastics are fibres from our clothes, and that stuff is working its way up the food chain.

“And we don’t need it, this is the thing.”

Grant, who runs textile firm Cookson & Clegg and Savile Row tailors Norton & Sons, has launched his Community Clothing Organic Athletic range, which uses only plant-based fabrics.

And he insisted that even within sport there is no need for elastane, adding: “Seb Coe 1980 Olympics won the gold medal wearing entirely natural clothing, there was no elastane in anything that he wore then.

“He set a world record that today is only three per cent faster.

“And that includes all the changes in nutrition, the changes in training, everything else that you add in that will also have improved those times.

“It’s a miniscule change. So actually the performance side of it is really not that great.”

Lack of scientific research

Grant said that although natural rubber is an alternative to elastane, it is expensive, but as yet there are no cheap solutions, and manufacturers have slashed the scientific research teams who might have found one.

He said: “So many people in our industry have a background which is on the arts side and the creative side of fashion, and very few these days have a background in the science and engineering side of fashion.

“There are a lot of people outright just telling fibs – it took us (his community clothing line) nearly five years to develop all of the different bits that went into this product because everybody had stopped doing it.

“Simple things like the elastic that goes into the waistband. The elastic in running shorts is elastane, which is an oil-based polymer, and nobody was making a natural rubber waistband elastic.

“The stretch in sportswear comes in various different guises. You have the mechanical stretch in the fabric – so a knitted jersey is made of lots of interlocking loops and when you pull them they stretch apart and when you take the force away they relax.

“That stretch has a certain amount of recovery which for years and years was fine.

“Today we have added to that the chemical stretch that you get within something like elastane, where you get polymer chains being elongated and recovering, which gives you that kind of tight, quick recovery that we’ve all got used to in running tights, cycling shorts, all of that sort of stuff.”