LONDON (Reuters) - Law firm Quinn Emanuel has filed one of two lawsuits in Germany against Volkswagen for institutional funds in claims that could run into billions of euros over the carmaker's emissions test cheating scandal, litigation funder Bentham Europe said on Tuesday.

"The breadth of the shareholder base that is represented by Quinn Emanuel should be a wake-up call to Volkswagen AG that it needs to engage with shareholders now, resolve matters and concentrate on regaining its market share," said Jeremy Marshall, chief investment officer of Bentham Europe.

The so-called 'Dieselgate' scandal has forced out Volkswagen's (VW) <VOWG_p.DE> previous chief executive, tarnished one of Germany's most renowned corporate brands and driven down VW's share price since it erupted last September.

Bentham Europe, which plans to publish more information after the second lawsuit is filed in Germany, said the claims related directly to the sharp fall in VW's share price in the week beginning Sept. 21, 2015.

It said the lawsuits were representing a "true cross-section" of the investor base of the embattled company, from sovereign wealth funds and international asset managers to public and multinational company pension funds, including the California State Teachers' Retirement System (CalSTRS).

VW, which is facing a handful of investor lawsuits, admitted last September it had cheated U.S. diesel emissions tests and that illegal software could be installed on up to around 11 million vehicles worldwide.

(Reporting by Kirstin Ridley; Editing by Mark Potter)