The costs of car license plates in Shanghai increased by more than 10,000 yuan ($1,600) in the city's latest auction, forcing the government to put back a price ceiling for the next two months.

The steep surge, coming after the government scrapped the price ceiling in October, upset many consumers. But experts said the price of plates, dubbed "the world's most expensive sheet iron", will continue rising in the long term, given the growing demand for car ownership and the city's limited traffic capacity.

According to the city's policy on car license plate auctions, a price ceiling will be applied for the following month if the average cost of a plate increases at least 3 percent, and for the next two months if the average cost is at least 6 percent. The price ceiling is the weighted average price for the most recent three months.