The European Commission Wednesday repeated its warning to Germany that it will carefully scrutinize any state aid provided to carmaker General Motor Co.'s European arm, Adam Opel GmbH to ensure it follows the European Union's strict rules on state aid.

The commission will look into reports that a number of European governments are negotiating over the financial support for Opel, and possibly linking the aid to the number of workers finally retained by New Opel in different countries, it said.

"The European Commission will not accept state aid that is conditional upon the implementation of a specific business plan, previously negotiated with member states, which defines the geographic distribution of restructuring measures," said the commission's spokesman on competition matters, Jonathan Todd.

Managers of the Opel business must be allowed to revise any plans to ensure that it can slim down its operations as required to ensure the long-term viability of the company, the commission said.

The German government has promised EUR4.5 billion in public financing for Opel but the bailout package has prompted fears from other states with Opel plants, or plants operated by its sister brand Vauxhall, that it will be conditional on keeping German plants open at the expense of more efficient plants elsewhere.

-By Carolyn Henson, Dow Jones Newswires; +32 2 741 1481; carolyn.henson@dowjones.com