Cocaine claims could cost Jodie Kidd £500,000 in model contracts

Miss Kidd, 28, has so far kept quiet about allegations that she admitted using the drug herself and boasted of knowing a string of dealers.

Her agents - who have also refused to comment - have previously cultivated a wholesome, sporty image for their client, who is well-known for her aristocratic connections, including her friendship with Princes William and Harry.

But now three major firms she has promoted this year - Marks & Spencer, Hi-Tech sports shoe and LG Electronics - have moved quickly to emphasise that they all took an 'anti-drugs' line.

If just this trio were to sever their ties to Miss Kidd, it would cost her at least £375,000 in fees. And other firms could follow.

Scroll down for more...

The strongest hint of such a cooling in relations came from Marks & Spencer, which uses the 6ft 1in polo-playing blonde to promote its financial services.

M&S chief executive Stuart Rose, said: "I don't know what the facts are - but I condemn all drug users."

Hi-Tech, which has a range of women's golf shoes designed with the help of Miss Kidd, said: "It goes without question that our company does not condone drugs."

LG Electronics, which used Miss Kidd to promote its eco-washing machine earlier this year, observed that a reputation for cocaine use is "not a thing you would want in a brand ambassador".

Scroll down for more...

Boots, which used Miss Kidd for its Quit Smoking campaign earlier this year, said pointedly: "Careful consideration is always given before Boots work with any celebrities."

Other firms connected to the former public schoolgirl, who lives in a variety of homes including a £600,000 farmhouse in Billingshurst, West Sussex, have been refusing to comment.

Miss Kidd met the undercover reporters believing them to be potential investors in a polo club she is trying to set up.

The News Of The World claimed Miss Kidd obtained three grammes of cocaine for £150 for the undercover reporters.

Asked whether the cocaine was good quality, Miss Kidd allegedly said: "I'd do it. I'm not going to do s***. It's not the best but it's what we can do at half past 12 at night."

Anti-drugs campaigners say celebrities who use cocaine set a damaging example to impressionable young fans.

Should the claims be substantiated, this could make Miss Kidd's employers anxious about a knock-on effect on their own reputation.

Miss Kidd will be well aware, however, of how fellow British model Kate Moss spectacularly bounced back after being covertly pictured snorting cocaine in September 2005.

Initially, Miss Moss lost advertising contracts.

But she has since managed to capitalise on the 'edgier' image the furore gave her, obtaining the enthusiastic backing of Stuart Rose's retail rival, Top Shop boss Philip Green, with whom she launched her own clothing range.

Indeed, asked by the undercover reporters how she thought the cocaine incident had affected Miss Moss's career, Miss Kidd is said to have replied that it had made it 'ten times better'.