The NCB Purchasing Managers' Index registered 53.3 in December to signal a further expansion in the manufacturing economy.
But the pace of growth slowed slightly to a 21-month low, reflecting a downturn in the pace of growth of export orders.
The PMI is the result of a survey of 250 manufacturing companies. Readings above 50 signal growth, below 50 contraction.
Output and new orders again increased in December, but a s lower rate than in November. The benefits to exporters of a weak euro were offset by an easing of demand from the UK, US and continental Europe.
