Volkswagen has gone on trial in Germany in what is the first court case against the carmaker over the diesel scandal.
Investors are pursuing VW for about €9.2bn (£8.2bn) in damages, claiming the company should have come clean sooner about falsifying emissions data.
VW shares crashed after disclosure in 2015 that its diesel technology emitted illegal levels of pollution.
"VW should have told the market that they cheated," Andreas Tilp, a lawyer for the plaintiffs, told the court.
"We believe that VW should have told the market no later than June 2008 that they could not make the technology that they needed in the United States," he told the Braunschweig higher regional court.
Shareholders representing 1,670 claims are seeking compensation for the near 40% slide in Volkswagen's share price triggered by the scandal, which broke in September 2015 and has cost the firm €27.4bn in penalties and fines so far.
The legal action has been brought by the Deka investment fund, which is being used a template for a further 1,600 lawsuits.
The case involves about 50 lawyers, and interest in the hearing is so great that it had to be moved from the court house to a nearby conference centre.
In a short statement to the BBC, VW pointed out that the "lawsuit is solely and exclusively about whether Volkswagen complied with its disclosure obligations toward shareholders and the capital markets".
The company said it was "confident" it had carried out its obligations correctly.
The court case is expected to take at least until next year to be fully decided.
Former executives from VW, Porsche and their sister company Audi are under criminal investigation in Germany.
The company itself has already been fined €1bn by German prosecutors over its diesel emissions scandal. It has also paid a fine of $4.3bn in the US to resolve criminal and civil penalties.
VW has admitted its responsibility for the diesel crisis.