Britain's biggest ice cream manufacturer admitted this week it would have to slash the number of special offers on its brands such as Cornetto, Magnum and Carte D'Or - during the crucial summer season.

Unilever blamed manufacturing problems at its central distribution plant in Gloucester. These had resulted in supply problems to retailers, the company said.

"The problem originated from a broken crane at our new cold store facility in Gloucester, which impeded the speed at which we were able to distribute our ice cream, and was exacerbated by the spike in demand caused by the warm weather," a spokesman told The Grocer.

"Due to the difficulties this has caused, we have informed customers that we are reducing ice cream promotional activity in June while we seek to rectify the situation. We would like to sincerely apologise to our customers for this inconvenience and assure them that we are working hard to fix the problem."

The revelation was especially embarrassing for Unilever as it came in the middle of the first-ever National Ice Cream Week.

Cheshire-based Fredericks Dairies claimed it would double manufacturing from 12-hour shifts to 24-hour production to meet the increased demand from retailers following Unilever's problems and the recent hot weather.

Fredericks said it was experiencing exceptional demand for Cadbury Dairy Milk ice creams and Del Monte Smoothie ice lollies.

"We are seeing some serious lolly action with all the publicity surrounding the Daniel Craig lolly, and our rivals have hit melting point right in the middle of the first National Ice Cream Week," said company owner Frank Fredericks.

It is the second time in two years that Unilever's Gloucester site has been hit by problems. In July 2007 the company was forced to close the site after severe flooding cut off water supplies following a technical failure at a local treatment centre.