French manufacturing activity fell at the fastest pace in four months in January as new orders dropped the most since the global financial crisis, a survey showed on Friday, boding ill for the sector's outlook.

The Markit final manufacturing PMI came out at 42.9 for the month, down from 44.6 in December, well below the 50 mark separating expansion from contraction and unchanged from a preliminary estimate.

New orders fell at the fastest pace since March 2009, when France and much of the developed world was mired in recession caused by the global financial crisis.

Export orders fell less quickly than overall new business, suggesting that subdued domestic demand was the main culprit for the drop.

"The fact that new orders fell at the sharpest rate for nearly four years is a particularly concerning development and suggests further steep falls in output are likely as we progress throughout the first quarter," said Markit senior economist Jack Kennedy.

"Confidence seems to have evaporated in the face of an increasingly uncertain economic environment, leading manufacturers to make sharper cuts to employment, purchasing and input stocks," Kennedy added.

Manufacturing, which accounts for about 11 percent of French economic output, has long been one of the weakest spots of the euro zone's second-biggest economy, losing ever more jobs in the wake of successive waves of factory closures.

The sector's weakness is contributing to overall weakness in the 2 trillion euro ($2.7 trillion) economy, which economists polled by Reuters expect to stagnate over the course of 2013.

(Reporting by Leigh Thomas; Editing by Hugh Lawson)