Si's first lawsuit, requesting the authorities to reveal the auctions' income and spending, ended in failure in mid-January as the court ruled such information constituted 'state secrets'. His second case, demanding the authorities justify the auctions by showing related legal documents, was also frustrated at the same hearing.

In the third case he aimed to get the Shanghai Municipal Transport and Port Authority to publish its contract with the state-owned Shanghai International Commodity Auction, organiser of the sales.

'The whole auction process, which involves titanic amounts of public money, should be transparent, open and based on laws,' said Si, a lawyer at the Shanghai DeBund Law Offices.

He is not alone in his crusade. During the past six years, some senior central government officials and mouthpiece publications have slammed the Shanghai auction system and urged that its financial accounts be revealed.

However, Shanghai's government does not seem to have been too worried about defending itself against such criticism. It has only responded occasionally during the past few years, telling the Commerce Ministry that the city was using a market mechanism to fight the congestion, and another time publishing income and spending figures that still failed to account for a huge amount of money.

Not surprisingly, those responses have failed to convince members of the public to abandon their concerns.

Si's series of legal actions against the authorities signalled that people were becoming more aware of the importance of the government operating on the basis of the rule of law, a fellow Shanghai legal expert said.

'They resort to reasonable actions within the current judiciary system, such as applying for administrative reviews and suing the department,' East China University of Political Science and Law professor You Wei said.

Si's third lawsuit was accepted by the Huangpu District People's Court on March 15 but he lost the case on April 29 .

He had initially applied for access to the contract. The authority replied in October, saying authorisation letters for all auctions had been made available on the transport authority's website since September 2004 and no further related documents existed.

However, all those authorisation letters were short and simple, giving only the auction time and quantity of licence plates to be sold, Si argued.

That was when he decided to launch a legal attempt to push for more openness. 'I don't believe there is no contract, which is more formal than a simple authorisation letter and should contain details such as commissions and the auction company's responsibilities as well as penalties if there is any fault,' he said.

If the court confirmed that no such contract existed, he said, the municipal government should be asked why no formal document was signed for such a huge deal.

Shanghai is one of the mainland's most seriously gridlocked places.

Experienced drivers complain that every hour in the city is a 'peak hour' and local media have reported that vehicles in central Shanghai can only travel at 10km/h on some days.

The main disadvantage for non-Shanghai-registered vehicles is a ban on driving on elevated roads - key transport channels in the city - during rush hour.

Every month, about 26,000 people vie for just 9,000 vehicle licence plates. Many see a plate number starting with the character hu, meaning Shanghai, as a status symbol that could appreciate in value. So far this year, average prices have hovered around 45,000 yuan, but a licence plate up for resale can fetch upwards of 50,000 yuan, Hexun.com reported.

In December, prices surprisingly plummeted to just 10,000 yuan, triggering speculation of under-the-table manipulation. Calls to supervise the auction scheme have since increased.

You said he was not confident about the mainland judiciary's independence, but if people who tried to challenge the government always lost their lawsuits, it would not advance social stability because they would give up on reasonable actions and resort to rebellion instead.

He called for a national law on such auctions, since other cities were looking at following Shanghai's footsteps in tackling road congestion.

Another controversial system is in Beijing, where a lucky draw to allocate licence plates has sparked complaints that it is limiting people's rights to buy cars and could benefit scalpers.