MILAN — Italian auto maker Fiat SpA on Tuesday said Andrea Formica resigned as head of its namesake Fiat brand amid a management overhaul following its acquisition of a majority stake in Chrysler Group LLC.

Although Fiat didn't elaborate, industry analysts suspect Mr. Formica's departure, effective Sept. 1, was likely due to the auto maker's poor sales performance in Europe, its traditional market, reported The Wall Street Journal.

Mr. Formica, 50 years old, couldn't immediately be reached for comment. Fiat confirmed reports in local newspapers of his impending departure.

Mr. Formica joined Fiat in September 2010 after leaving Toyota Motor Corp.'s European operation, where he was senior vice president of sales, marketing, product planning and communication.

In addition to being chief executive of the Fiat brand, he was also responsible for sales at the Fiat's two other brands: Lancia and Alfa Romeo.

However, when Fiat announced at the end of July the creation of a new executive team, called the Group Executive Council, it didn't include Mr. Formica among its members. It instead named Olivier Francois to head the Fiat brand.

Mr. Francois is already head of marketing for all of the Fiat and Chrysler brands. His additional title as head of the Fiat brand will be different from the one held by Mr. Formica because it will focus on brand development. The new team, which will oversee the operations at both Fiat and Chrysler, comes into effect on Sept. 1.

Another of Mr. Formica's responsibilities, sales in Europe, will be taken up by his predecessor, Lorenzo Sistino, who joins Mr. Francois as member of the new management team.

Mr. Formica arrived at Fiat as government incentives for the purchase of small, environmentally friendly cars expired and concerns persisted about the economy, contributing to a drop in auto sales across Europe. He also had to deal with a relatively small offering of new models, the sports utility vehicle Freemont being one of them.

In the first six months of 2011, Fiat was the worst performer among Europe's top six auto makers in terms of sales. Combined sales of Fiat, Lancia and Alfa Romeo cars tumbled 13 percent and the auto maker's share of the European Union market fell to 7.3 percent from 8.2 percent for the same period last year, according to figures from the European Automobile Manufacturers' Association.

Even Mr. Formica's troubled former employer, Toyota, did better than Fiat, with sales falling 8.2 percent. Fiat owns 53.5 percent of Chrysler on a fully diluted basis.