By Foo Yun Chee and Benoit Van Overstraeten

BRUSSELS A U.S. economist chosen for a senior European Union antitrust job pulled out on Wednesday after her appointment triggered criticism from the president of France and some EU lawmakers.

Fiona Scott Morton, chief economist at the U.S. Department of Justice during the Obama administration, had been due to take up the post as chief competition economist at the European Commission on Sept. 1.

"Professor Fiona Scott Morton has informed me of her decision to not take up the post as chief competition economist," EU antitrust chief Margrethe Vestager, who had announced the appointment a week ago, said in a tweet.

Vestager said she accepted Scott Morton's decision with regret.

Scott Morton, 56, was supposed to advise the European Commission on its investigations into Big Tech and its enforcement of a series of landmark rules to rein in tech giants.

"Given the controversy that has arisen because of the selection of a non-European to fill this position, and the importance that the Directorate General has the full backing of the European Union as it enforces, I have determined that the best course of action is for me to withdraw and not take up the Chief Economist position," Scott Morton said in a letter published by Vestager.

French President Emmanuel Macron and French lawmakers were the biggest critics of the new U.S. hire.

The French government stuck to its guns on Wednesday after Scott Morton's decision to quit.

French foreign ministry spokesperson Anne-Claire Legendre told reporters that Paris had been against Scott Morton's appointment because it potentially impacted the bloc's sovereignty and may hurt European businesses and consumers.

Legendre said in the future there should be more thought to recruitment rules especially where there could be conflicts of interests in the "most strategic and sensitive positions within the European institutions."

Namur University law professor Alexandre De Streel, one of 40 leading economists who backed Scott Morton, said Vestager could have handled the issue better.

"The Commission should have explained much better the difference between a technical advising role, for which Europe and its sovereignty will be best served by relying on the best expert in the world, and policy deciding role, for which nationality matters more," he said.

EU lawmaker Paul Tang from the Netherlands called for more transparency on conflicts of interest.

"Vestager needs to restart the procedure and include the possible conflicts of interests into the assessment of candidates right from the start," he said.

(Reporting by Benoit Van Overstraeten and John Irish; Editing by Charlotte Van Campenhout, David Holmes and Mike Harrison)