Businesses were threatened with an invasion of caravans on their car parks if they refused to pay a tarmac contractor's vastly inflated bills, a court was told yesterday.

Contractor Joseph Kennedy offered cheap deals to customers, but after his men had laid the tarmac he multiplied his demands nine times.

Kennedy, 40, who claimed to be working for the Highways Agency, said he had surplus tarmac they could have free with a labour charge as low as 90p a square metre.

But he later insisted that the price was for a square foot.

His ruse was exposed after he told a cafe owner in Burneston, North Yorkshire, he was resurfacing the A1 and she signed for 30 loads of tarmac, before reporting his demands to the North Yorkshire Trading Standards office.

Kennedy made demands of £12,200 from four customers, but he was paid only £700 plus a car, Teesside Crown Court was told.

The owner of a vehicle repair shop in Bolsover, Chesterfield, was told his bill would be £500 to £600, but was so scared by Kennedy's screamed demands that he twice gave him a cheque for £5,181.30. He later stopped the payment.

Kennedy also offered free chippings to the manager of a bagel factory in Leeds at £2 a square metre, but he later demanded £2,450 for a square foot rate.

He billed three factory units in Coventry for £2,400 after agreeing a price of £400.

Simon Kealey, prosecuting, said: "He threatened a man saying that he would put his caravans on the site if he did not pay."

Kennedy, of Sutton Road, Askern, Doncaster, South Yorkshire, pleaded guilty to four charges of blackmail by demanding money with menaces between February and October last year and also making a false statement.

Judge Peter Armstrong told Kennedy he was facing prison after he was released on bail for pre-sentence reports.

A confiscation of assets hearing will take place in March.

North Yorkshire county councillor John Fort said: "This man subjected businesses all over the country to threats and intimidation. Once again, our trading standards service has intervened to stop these intolerable practises and protect legitimate businesses."

Head of trading standards Graham Venn said: "It should be clear to all those who wish to trade in this manner that their behaviour will not be tolerated. We will take a tough and thorough stance to ensure they are brought to justice."