A coalition of lawyers’ groups called on Attorney General Martha Coakley Wednesday to step aside and appoint an independent investigator to direct the inquiry into the state drug lab where former state chemist Annie Dookhan is ­accused of tampering with evidence in criminal cases.

Coakley’s office is spearheading a two-track inquiry ­into the former Department of Public Health lab in Jamaica Plain: the criminal inquiry of Dookhan and a deeper look ­into thousands of cases handled by other chemists at the lab closed by the Patrick administration this year.