Sonja Farak, 37, who worked for Amherst laboratory and admitted ingesting samples, was high on methamphetamines, ketamine, cocaine, LSD and other drugs were – even when appearing in court.

A spokeswoman for the attorney general, Maura Healey, said that the news “will no doubt have implications for many cases”.

She said: “We are deeply concerned whenever the integrity of the justice system is called into question or compromised.”

Luke Ryan, defending, told the Boston Herald that Ms Farak dealt with 30,000 cases between 2005 and 2013.

He said: “This is a statewide scandal, and I think it’s going to take an enormous toll on the system.”

Another lab worker, Annie Dookhan, who faked test results at a Boston lab and was jailed for three years in 2013, threw 40,000 cases into doubt.

The American Civil Liberties Union of Massachusetts (ACLU) said Ms Farak’s misconduct could rival that figure.

Matthew Segal, legal director of ACLU, said: “It’s now beyond doubt that the drug war in Massachusetts during the Dookhan-Farak era was built on a foundation of falsified evidence.”

He added that prosecutors “have an obligation to identify and notify everyone who might have been denied due process”.