FILE PHOTO: An Aston Martin logo is displayed at the 89th Geneva International Motor Show in Geneva, Switzerland March 5, 2019. REUTERS/Pierre Albouy/File Photo

LONDON (Reuters) - The biggest investor in Aston Martin AML.L offered on Friday to buy another 3% stake in the luxury carmaker, whose shares have slumped since listing last year.

Strategic European Investment Group, part of the Italian private equity group Invest industrial, already owns 31% of Aston Martin. It only wants to buy a maximum 3% more, but has to make an offer to all shareholders due to its already large holding. It confirmed it is offering to pay 10 pounds ($12.53) per share.

Aston Martin has struggled since it listed in October last year. Its shares, down 21% so far this year, closed Thursday at 963 pence, valuing the business at 2.18 billion pounds.

The company’s recent results have been hit by a need to invest more in its manufacturing plants and expand its vehicle offering, leading to higher costs.