Irish Sugar began closing its plants in Carlow and Mallow last night in response to the withholding of supplies by farmers in a row over the price of beet.

There was no immediate move to lay off any of the 600 workers at the two factories. If the dispute is not settled quickly, however, some staff are likely to be placed on protective notice next week.

The closures were marked by an acrimonious exchange between the Greencore-owned company and the Irish Farmers' Association, whose members began withholding beet supplies on Wednesday.

IFA president, Mr Tom Parlon, accused Greencore of arrogance and intransigence and said it was using its monopoly to negotiate "by diktat, threats and victimisation". Irish Sugar responded by claiming the IFA was preventing farmers from supplying beet. "We know from our contact with growers that the vast majority of them wish to resume supply to the Carlow and Mallow factories," said the company's chief executive, Mr Seβn Brady. This was denied by an IFA spokesman, who said there was "solid support" for the action among beet growers.

An 11th-hour effort by Carlow-based Fine Gael TD, Mr John Browne, to broker a resolution failed. Mr Browne spoke to both management and farmers' representatives yesterday and said both appeared to be prepared to enter talks.

Closing down the factories and re-opening them were not simple operations, Mr Browne said, and at least three to four days' production would be lost, which was "serious". Asked about the implications for staff, an Irish Sugar spokesman said the company could "not believe that the IFA would allow farmers to go over the cliff edge" and cause jobs to be lost.