France's Societe Generale said it was in talks with unions to finalise a plan to cut jobs at its corporate and investment bank, with one union source saying at least 500 jobs could go.

SocGen and larger rival BNP Paribas, whose shares are trading at deeply depressed valuations as the eurozone debt crisis rages, have announced asset sales and warned that jobs will have to go as they seek to plug an estimated capital shortfall of 8.8 billion euros ($12 billion) without outside help.

A spokeswoman for SocGen said the bank's management had met with trade unions on Tuesday morning and talks would continue in the afternoon, confirming information from union sources.

But she would not confirm a number of job cuts of "between 500 to 600" given by one union representative.

"It is premature to give more details on the staff adjustments that will be necessary at the corporate and investment bank, in France and abroad," she said.

A union source told Reuters: "We are negotiating the layoff plan ... staff are very worried. (The number of cuts is) between 500 and 650."

Another union representative said SocGen Chief Executive Frederic Oudea, who rose to the top spot after the Jerome Kerviel rogue trading scandal almost brought the bank to its knees in 2008, had met with unions earlier on Tuesday.

SocGen's investment bank, which employs some 12,000, has already been cutting staff at the margins since the summer, according to employee sources, following a drastic loss of confidence from US money markets in European banks.

French labour laws strictly regulate how layoffs can proceed and French banks are seen leaning towards voluntary departure schemes, less costly than straightforward firings. ($1 = 0.734 Euros)