(Adds background, analyst comment)
LONDON, Feb 24 (Reuters) - Investment bank Lehman Brothers is placing 3.6 million shares, or a 1.26 percent stake, in French auto maker Renault on behalf of French media group Lagardere , dealers said on Monday.
The shares are being sold via a quick auction to institutional investors, known as an accelerated bookbuilding process, they said.
Renault declined comment, while both Lagardere and Lehman Brothers were unable to comment immediately.
At 1040 GMT, shares in Renault were off 2.23 percent at 38.95 euros.
Lagardere was one of a group of French firms that took a stake in Renault when shares in the automaker were sold on the market in 1995.
Through its Matra Automobile unit, Lagardere has produced a number of vehicles for Renault. But last year Renault grabbed back production of its Espace van from Matra, leaving the Lagardere unit with only the Avantime coupe to manufacture at its plant at Romarantin in central France.
The futuristic Avantime has had lacklustre sales, with only 30 of the models coming off assembly lines each day. Last year, sales at Lagardere's auto unit slumped 31 percent to 782 million euros.
Last week, Lagardere chief Jean-Luc Lagardere resigned from the board of Renault in a move many viewed as a prelude to a more formal split.
"This has been talked about for quite some time," said Stephen Reitman of Merrill Lynch. "It is better that the (share) overhang is dealt with."