New figures from the Central Statistics Office show that production among manufacturing industries fell by 13.9% in September from August.
On an annual basis, production in September decreased by 13.7% compared to the same month last year.
Today's figures show that the modern sector, which is made up of a number of high-technology and chemical sectors, showed a monthly decease of 22.4% in September.
The biggest change was in basic pharmaceutical products and preparations which slumped over 35%.
September also saw a 1.3% decline in the traditional sector.
Stockbrokers Merrion described today's industrial production figures as ''very disappointing''. They noted that the annual decrease of 13.7% was the biggest annual decrease since November 2009.
''While external factors don't look particularly encouraging for the manufacturing sector at this point in time, Ireland's focus on relatively recession-hardy exports such as pharmaceuticals and its improving competitiveness should help it weather the storm better than most,'' Merrion's economist Alan McQuaid said.
He said that based on the latest purchasing managers index, he believes the Irish manufacturing sector will post an overall increase in output for the third year in a row in 2012, albeit another modest rise of less than 1%.
