French police struggled to impose anti-pollution measures on motorists around Paris on Thursday as the city remained shrouded in smog during its worst winter pollution in 10 years.

Since Tuesday, officials in the Paris region have ordered half of all private cars off the road, alternating between a ban on registration plates ending in odd or even numbers.

But the local air-monitoring service AirParif has cast doubt on the effectiveness of the restrictions and AFP reporters saw many motorists flouting the ban on Thursday.

"I wasn't going to buy another vehicle to go to work today!" said 31-year-old builder Jug who was waiting in his truck to pay a fine of 22 euros ($24) after being stopped by police.

Traffic jams in the morning rush hour were 415 kilometres (258 miles) around Paris, compared with 300 normally, local road traffic officials reported.

France's Environment Minister Segolene Royal, who has been criticised in several newspapers for failing to take action, announced cabinet-level talks to clean up transport on Saturday.

The surge in pollution around Paris and in other parts of France showed "that much more robust measures are indispensable", Royal told AFP.

Royal said new initiatives could include extending incentives for the purchase of electric cars.

She would also propose forcing motorists to display colour-coded air-quality certificates on vehicles so that the dirtiest of them could be banned during the next pollution alert.

The current spike in pollution offered a "good opportunity", said Royal, since people would be more willing to accept constraints having been made more aware of the problem.

For more than a week, the Paris region has been on pollution alert with levels of fine airborne particles known as PM10 consistently above 80 microgrammes per cubic metre of air.

Though high by local standards, the pollution is a fraction of levels in New Delhi, the world's most polluted capital, where PM10 was above 600 in some areas on Thursday.

The surge in pollution has been driven by cold weather and near windless conditions that have trapped exhaust fumes, smoke from wood fires and other pollutants.