Irate French farmers are threatening to bring Paris to a halt on Thursday by blocking arterial roads to the capital in the latest protest over tax hikes.

Two unions from the Paris region on Monday announced a "blockade on Paris," to "make the voice of the agriculture sector, which has been sacrificed, heard."

The FDSEA and JA unions said their members were being "bludgeoned" by tax rises as well as by "more and more demanding environmental norms, increasing checks and stronger regulatory mechanisms."

President Francois Hollande's government has already been forced to suspend the planned introduction of a new environmental "ecotax" on commercial vehicles carrying cargo more than 3.5 tonnes after violent protests in Brittany, a predominantly agricultural region in northern France.

Opponents of the tax, which critics say unfairly penalises remote areas dependent on deliveries by road freight, are demanding it be scrapped altogether.