The 54-year-old celebrity chef has been given a waiver to enter the country to make a television advertisement for a brand of chocolates next month.

Immigration New Zealand said Ms Lawson had been granted a work visa under the country's "special direction" laws, which was necessary because of her US travel ban.

A spokesman said: "As she has been excluded from another country, the United States, she was ineligible to be granted a visa to enter New Zealand unless given a special direction.

"A special direction was granted and her visa application was approved."

The statement was official confirmation that US immigration officials had prevented her boarding a plane at Heathrow for Los Angeles, where she had previously filmed the cooking talent show The Taste.

The mother of two was banned from travelling to the US as a result of comments she made about taking cocaine and cannabis while giving evidence under oath in last year's trial of two of her staff accused of fraud.

Ms Lawson told jurors she took cocaine twice, once with her late husband John Diamond when he found out he had terminal cancer and again in 2010 when, she said, she was being "subjected to intimate terrorism" by her former husband, Charles Saatchi.

But she told the court: "I have never been a drug addict. I've never been a habitual user."

Police had reviewed the allegations of drug use that emerged during the trial but said no further action would be taken, despite public controversy over her admission.

Ms Lawson later told the US breakfast television show Good Morning America that having details of her acrimonious split from Mr Saatchi made public had been "mortifying".

The US can decide to bar visitors who have committed drugs offences even if they have never been charged.

The Telegraph, London