Local car owners are questioning the results of a government-funded survey about the recently renewed "no-car-day" policy, saying the findings might have been massaged.

The municipal government announced last Friday it was extending the no-car-day policy it launched a year earlier. The no-car-day policy will now continue for at least two more years, to April 2012.

The controversial policy has been attacked by some car owners and legal experts ever since it was introduced in 2008.

But authorities, citing statistics from a Beijing-based survey company, insisted last Friday that most people supported a continuation of the ban.

The restriction, that means cars with certain license plate numbers are barred from entering the urban area on certain days, had been due to expire on April 9.

The policy ensures Beijing's 5.8 million drivers are each prohibited from driving on one working day each week.

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The move blocks around 20 percent of cars from potentially being driven each day. Authorities say it has reduced traffic by more than seven percent.

The survey, conducted by Beijing-based Horizon Research on behalf of the authorities, quizzed more than 2,500 people last year and showed 83.6 percent supported an extended ban.

Analysts from the private research group said 60 per cent of respondents to the survey were car owners.

The same research body also said last December in another survey that Beijingers were wasting seven more minutes each day fighting traffic on busier roads than they were two years earlier.

But similar surveys from other sources have shown different results.

An online survey of 1,200 readers of Beijing News, a popular daily newspaper in the capital, showed as many as 94.7 percent were against the continuation of the car ban, saying hot sales of new cars mitigated any success the policy had in taking cars off the streets. Eighty percent of participants in that survey were car owners.

Another survey, by the popular Internet portal Sina.com, showed 83.1 percent of respondents did not want the car ban to be continued. More than 82 percent of participants of that survey were from Beijing.

Some car owners were incredulous about the latest survey.

"I can tell you right now, hardly any car owners will support such a ban," said Tang Ying, a travel agent who was parking his car near Wangfujing on Monday. "Everybody knows the ban has failed to remove any traffic. The government must have manipulated the results to support their claims, as is always the case."

Beijing's car population exceeded four million last December after increasing by more than 550,000 last year. The number now stands at more than 4.17 million and 2,000 new cars are hitting the roads of the capital each day.

Potential car buyers also told METRO that no-car-day restrictions were part of the reason why they were looking at buying second cars.

Mao Baohua, a government adviser on transportation policies, has said that the number of cars in Beijing is already out of control, leaving the authorities with limited choices that include car bans and raising congestions fees.

But Beijing's transportation chief, Liu Xiaoming, said last month that the city had no plans to restrict car ownership.