China has used an opaque bidding process, favoritism and other practices to effectively shut European companies out of the country's huge public procurement market, the European Union Chamber of Commerce in China said in a study released Wednesday.

The chamber report, based on surveys of 50 European companies, adds to a growing chorus of complaints from major trading partners about China's "fragmented, inconsistent, and unevenly implemented" procurement system.

The stakes of state procurement bids are particularly high in China. The study estimates Chinese government procurement – defined to include everything from infrastructure projects to purchases by state-owned enterprises – is worth about $1 trillion, or more than 20 percent of its economy.

Chinese officials have frequently promised equal treatment for foreign firms. Chinese President Hu Jintao made the topic a theme of his January trip to Chicago and Washington, where he expressed his support for reform, fairness and transparency to American business leaders and calling Chinese intellectual property and government procurement policies fair.

Foreign executives, however, remain skeptical about China's progress on bidding prodecures. Gilbert van Kerckhove, head of the EU Chamber's public-procurement workgroup, said the problem lies with the central government's implementation of bidding regulations nationwide.

"They should have better implementation," Kerckhove told the Wall Street Journal. "We are not na?ve. We know at times there are going to be protectionist measures, but this has nothing really to do with China's bidding law."

Although the region's trade deficit decreased slightly in February, European bureaucrats remain concerned by the EU's growing current account surplus with China. The EU27 deficit with China in January increased to €15.7 billion from €12.3 billion last year. EU trade commissioner Karel de Gucht said last year he would introduce legislation in 2011 to pressure China to expand European access to Chinese bids for public contracts. European leaders also raised the topic in meetings with Chinese Premier Wen Jiabao last year.

China submitted a revised bid last year to join the World Trade Organization's Agreement on Government Procurement, a preliminary step towards reforming its bid procedures to adhere to international standards.

Kerckhove hopes the efforts lead to stronger economic cooperation between Europe and China.

"Europe's attitude toward China is not to complain about trade imbalance and the yuan issue." Kerckhove said. "We are happy to have the imports from China, because they are cheap and good. We just want fair market access."