Almost one year since the New South Wales Government re-introduced a toll on the M4 motorway, drivers are turning off in droves to avoid paying the charge between Parramatta and Homebush.

New figures reveal that since the toll was reintroduced there are on average 42,000 fewer vehicles using the motorway each day.

The decline could cost the NSW Government up to $70 million in missed revenue annually.

Many motorists are exiting the M4 at Church St and either driving back roads or 'rat runs' or opting to take the toll-free Parramatta road.

The ABC spoke to dozens of motorists at the congested Church street exit of the M4 on Thursday morning, who all refused to take the toll route.

"I reckon it sucks, I mean we pay a petrol tax and they still want to charge tolls and they keep going up and up," Martin, a truck driver, said.

Another couple who travel from Penrith into the city twice a week also avoid the tolls because it was simply too expensive.

"The amount of money you have to pay going in and out of the city each day, $10 a day, that's $50 a week — who can afford it?"

The 7.5 kilometre stretch of road is charged on distance-based tolling.

The maximum is $4.74 for cars and $14.22 for trucks.

The State Opposition and media outlets have been asking the Government for months to provide daily figures on the number of vehicles using the new toll road.

The Government had previously refused to release detailed information on weekly traffic saying it would "significantly prejudice negotiations" around the sale of a 51 per cent stake in WestConnex.

However figures provided on Thursday by the Government show a steady decline in the number of vehicles using the M4 between Parramatta and Homebush over the past 11 months.

In July 2017, before the toll was introduced, an average of 196,000 vehicles used that section of the M4 per day.

But for the past two weeks of May, that number has dramatically fallen to 154,000 cars and trucks per day.

Western Sydney 'can't afford' toll

Shadow transport minister Jodi McKay said these figures showed that the Government was not listening to the people of western Sydney.

"The Government has hidden these figures until now and it's now clear why they didn't want anyone to see them," she said.

The Berejiklian Government has previously said any decline in vehicles numbers was only temporary and that drivers would return to the M4.

The Government also said the business case projections were for 164,000 cars per day by 2031.

NSW Premier Gladys Berejiklian said using the toll road saved motorists time and the Government was "really pleased with the progress of the M4 widening and the number of people actually using that road".

But Ms McKay said the figures showed that people living in western Sydney were not using the road "because they simply can't afford it".

Labor says the toll on the new widened M4 should be removed before 51 per cent of WestConnex is privatised.