Rural businesses could be left counting the cost under radical new plans by the Royal Mail to alter delivery times.

The market town of Thirsk in North Yorkshire has been chosen as one of 14 areas across the country where pilot trials of new "delivery patterns" will be carried out.

The trials, to be launched in the spring, will mean a single delivery, six days a week, to addresses in the area.

The intention is that those addresses which receive large amounts of mail, primarily businesses, will get deliveries before 9am, while others will receive their post before lunchtime.

Second deliveries, of which there are currently only tiny percentage in the Thirsk area, will not be carried out.

Yesterday's announcement led to immediate fears being raised locally that rural businesses would lose out under the move, with early deliveries being concentrated in the towns.

The chairman of Thirsk's Chamber of Trade, Don Hubbard, said: "This is very worrying and those businesses out in the country may well suffer.

"There are a lot of rural businesses around Thirsk and for the Royal Mail to deliver early to them and then go out later in the morning to deliver to domestic addresses would not make sense.

"Delays cost businesses money and a lot of points will now have to be clarified by the Royal Mail."

The Royal Mail said it was reviewing its delivery services in a move to increase efficiency as more of its markers were opened up to competition.

The review is aimed at driving down costs and boosting the reliability of mail in an effort to ensure more first class post arrives on time.

"Royal Mail has to deliver a reliable universal service to everyone for the price of a stamp, including to many places where the cost of that service is considerably more than 27p," said a spokesman.

"The regulator is increasing the pressure on Royal Mail with the proposal to open the most profitable elements of the market to competition in just a few weeks time.

"Our delivery patterns have not changed for many years and we believe there is scope to increase efficiency and improve reliability."

Consumer watchdog Postwatch said any changes should respond to customer views and needs instead of just meeting the aims of postal Consignia to save money.