(Reuters) -Shares in Stellantis slumped as much as 8.9% on Monday, hitting their lowest in more than two years, after CEO Carlos Tavares resigned abruptly on Sunday, deepening investors' worries about the turnaround of the world's No. 4 carmaker.

His exit leaves a void at the top of the company at a time of tumult as management scrambles to get rid of overcapacity and big inventories in the U.S., while global car demand remains sluggish and competition from Chinese rivals intensifies.

Previously regarded as one of the most respected executives in the auto industry, Tavares' approach came under scrutiny after slumping sales in North American led the automaker in September to issue a profit warning on its 2024 results.

Stellantis said it would seek a replacement CEO in the first half of 2025, and would establish a new interim executive committee led by Chairman John Elkann.

"This sets an unprecedented challenge for investors looking to invest in a firm with such volatility in the management team," JPMorgan analysts said in a note also referring to the earlier change of Stellantis' finance chief.

Stellantis' shares were down 7.3% by 0841 GMT, on track for their biggest one-day fall since end-September.

The stock, down 45% year-to-date, was the biggest faller among most peers in Europe, with the STOXX 600 autos & parts index down 2.2%.

"The difficulties of Stellantis continue to cast doubts about the global brand conglomerate business model... as well as CEO longevity in an industry as structurally and cyclically challenged as Autos," Jefferies analysts said

(Reporting by Enrico Sciacovelli and Alessandro Parodi; Editing by Amanda Cooper and Jan Harvey)