Workers at IBM's west Dublin circuit chip manufacturing plant have been told to take unpaid leave or holidays on three days in the next month.

More than 600 staff in the company's microelectronics division at Mulhuddart, west Dublin, will be affected by the decision to halt production.

The plant generally operates 24 hours a day, seven days a week.

The move will not affect 1,600 other workers at the company's operations in Mulhuddart. IBM employs 4,500 people throughout the State.

A spokesman stated the decision to halt production was part of IBM's "normal business model", saying resources were used to match targets.

These differed at different times of the year, he added. The division was generally very busy at the end of the year and it suited managers that staff take holidays at this time of year.

The spokesman denied staff had been asked to work a four-day week.

The plant will close on two consecutive Mondays this month - July 16th and July 23rd - and on Monday, August 13th.

When asked if the decision to halt production was taken because inventories were too high or demand low, the spokesman said: "Basically, we have a seasonal programme of production and we're in a general business-as-usual mode . . . I'd be interpreting it as part of a production model rather than an exception."

He added the company had closed on two days last summer for similar reasons.

Such stoppages enabled the company to maintain its systems.

There was no production last Monday because the company granted workers an "IBM day" for which they were paid but not obliged to work.

IBM staff were entitled to two such days each year, he said, with the second generally awarded later in the year.

This was in addition to normal holiday entitlements.

The spokesman said he believed staff were informed of the decision to halt production early in June.

Meanwhile, IBM - which confirmed last week it was laying off nearly 1,500 workers in its global services unit - is letting other employees go in its personal computer business and its sales and distribution operation.

A website of Alliance at IBM - a unit of the Communications Workers of America union - said sales and distribution employees in many locations "have just been notified of 30 days until termination".

"We're hearing of sales and distribution cuts, about 540," said Mr Lee Conrad, national organiser for Alliance at IBM and a former IBM employee. "I think this is just the tip of the iceberg."