BRUSSELS, March 5 (Reuters) - EU antitrust regulators are seeking a chief economist to help bolster their competition and merger cases, with the job open only to Europeans, a year after their pick of an American triggered a French backlash.

EU antitrust chief Margrethe Vestager's choice of Fiona Scott Morton, chief economist at the U.S. Department of Justice during the Obama administration, subsequently pulled out after French President Emmanuel Macron and some EU lawmakers criticised her appointment.

Critics pointed to possible conflicts of interest as Scott Morton had previously advised Big Tech as a consultant while others cited European sovereignty for opposing the hiring.

The chief economist vacancy, published in the EU Official Journal on Tuesday, said candidates for the three-year post must be a citizen of an EU country.

The successful candidate will lead a team of about 29, helping EU competition enforcers evaluate the economic impact of mergers, antitrust cases, tech regulations and foreign subsidies.

The post has been vacant since Aug. 1 last year after the previous holder of the job, Pierre Regibeau, retired.

The Commission's ongoing cases include Alphabet's Google, Meta, and Microsoft and enforcing landmark tech rules curbing the power of Big Tech. (Reporting by Foo Yun Chee; Editing by Chizu Nomiyama)