By Julia-Ambra Verlaine and Gabriele Steinhauser 

The European Union's executive on Wednesday tapped former French financial services commissioner Michel Barnier as the chief negotiator for the U.K.'s exit from the bloc.

The appointment of Mr. Barnier, who led the European Commission's overhaul of EU banking laws in the aftermath of the 2008 financial meltdown, was seen as provocative by some commentators in London, as France has taken a tough view on the U.K.'s future relationship with the EU.

Mr. Barnier will be a key figure in the negotiations over the U.K.'s divorce from the bloc, but not the only one. Didier Seeuws, a seasoned Belgian diplomat, was appointed last month as head of a Brexit task force by the European Council on which sit the leaders of the 28 EU countries. Meanwhile, the negotiations are likely to be directed by the bloc's leaders, including German Chancellor Angela Merkel.

Mr. Barnier, a 65-year-old center-right politician who has held numerous posts in the French government including foreign and agriculture minister, tweeted in English "Rendez-vous for beginning of demanding task on 1 October."

"I wanted an experienced politician for this difficult job," Commission President Jean-Claude Juncker said in a statement. "Michel is a skilled negotiator with rich experience in major policy areas relevant to the negotiations."

During his five-year tenure at the commission until 2014 in which he presided over the passage of more than 40 pieces of financial legislation, Mr. Barnier clashed with his British counterparts on a number of regulatory issues.

Officials who have worked with Mr. Barnier say he is a pragmatist, and in interviews he has repeatedly said he isn't an "ideologue."

While he has a reasonable command of English, Mr. Barnier strongly prefers to conduct business in French. When he appeared in front of the U.K. Treasury Select Committee in 2011 as EU financial services chief, he chose to testify in his native tongue after a brief statement in English--to the evident aggravation of some British lawmakers.

He also regularly confronted the City of London, especially when it came to EU rules around banker pay that capped bonuses and total compensation. The select committee lambasted him over bankers' pay, suggesting that restrictions on bonuses would cause a flight of talent to Asia and other global financial centers.

Officials close to him said that Mr. Barnier's experience with the select committee left a permanent impression, giving him the sense he had been the victim of unfair stereotyping.

In 2014, Mr. Barnier described his relations with then Chancellor of the Exchequer George Osborne as "never complacent, never easy, but constructive."

After serving as financial services commissioner, Mr. Barnier ran in 2014 for president of the commission but lost out to Mr. Juncker. During his campaign, he told The Wall Street Journal, "My line would be: less regulation in Brussels and more politics."

Mr. Juncker appointed him as special adviser on European defense and security in February 2015, a part-time, unpaid role. In his new job, he will report directly to Mr. Juncker.

Write to Gabriele Steinhauser at gabriele.steinhauser@wsj.com

(END) Dow Jones Newswires

July 27, 2016 09:02 ET (13:02 GMT)