Nigella Lawson may be forced to take a blood test before being allowed to travel to the US.

She was travelling alone and had cleared check in and security at London's Heathrow airport but was then told she couldn't get on the plane to Los Angeles and was forced to return to the first class check-in to collect her luggage.

Leading immigration lawyer Charlotte Slocombe told The Sun newspaper: "It will be the physician's job to determine whether or not she's a drug abuser.

"This includes an interview process and a possible blood sample.

"As long as the physician is certain that it's over a year since she took drugs, then she may get a visa.

"In theory, following the letter of the law, she could be inadmissible for a visa, full stop. It's complex."

It is thought US authorities had warned British Airways staff not to allow her to travel to California, as she would have been refused entry.

The country ask travellers if they have ever been arrested or convicted on drugs charges, and can prevent entry even if no charges were brought.

Nigella is expected to seek legal advice to help her get back into the US, which she visits regularly for both holidays and her work on 'The Taste'.

Her 'Taste' co-judge Anthony Bourdain was "mortified" with the decision not to let her into the US.

He wrote on Twitter: "I am absolutely mortified with embarrassment over the cruelty and hypocrisy of US actions re: #Nigella

travel. Unbelievable. (sic)"

Before adding: "Toronto mayor, Rob Ford? Welcome to the USA. Nigella Lawson? No. REALLY? Absolutely appalling misuse of our system. And by whom? How? (sic)"

Following the incident Nigella informed her fans she's taking a "holiday break".

She tweeted on Monday (31.03.14): "Off line for a while enjoying the ultimate; a holiday break with no signal! Will miss you all though. Know I will be eating on your behalf (sic)"