(Adds further details on court hearing, background on case, paragraphs 3-12)
BOSTON, Oct 24 (Reuters) - A Massachusetts judge on Thursday gave the state's attorney general the greenlight to sue Exxon Mobil Corp "ASAP" over allegations it concealed from investors and consumers its knowledge of the role fossil fuels play in climate change.
The ruling was a setback for Exxon, which had sought to delay the filing of the long-expected lawsuit by Massachusetts Attorney General Maura Healey until after the close of a trial over similar claims by New York's attorney general.
Suffolk County Superior Court Judge Heidi Brieger during a hearing in Boston acknowledged that Healey's office was required to give Exxon an opportunity to discuss the case at least five days before suing the company.
But she ruled that the state was under no obligation to wait longer than that after notifying Exxon on Oct. 10 of its intent to sue, which Assistant Attorney General Richard Johnston said his office wants to do "ASAP", or as soon as possible.
"We should be allowed to file our lawsuit at the earliest possible moment," he told the judge.
Exxon did not respond to a request for comment. In court papers, the company said Healey's decision to sue now after a three-year investigation was simply "gamesmanship" to distract the oil major's lawyers from the trial in New York that began on Tuesday.
Healey and her New York counterpart launched investigations into Exxon following news reports in 2015 saying company scientists determined that fossil fuel combustion must be reduced to mitigate the impact of climate change.
Those news reports, by InsideClimate News and the Los Angeles Times, were based on documents from the 1970s and 1980s. Exxon said the documents were not inconsistent with its public positions.
Healey in 2016 issued a so-called civil investigative demand to Exxon seeking documents to determine whether it had violated the Massachusetts consumer-protection law through its marketing and sale of fossil fuel products.
The company fought the records request, but the state's top court in April 2018 concluded Healey had jurisdiction to seek the records. In January, the U.S. Supreme Court declined to hear Exxon's appeal of that order.
New York meanwhile sued Exxon in October 2018, accusing it of engaging in a scheme to deceive investors about the impact that future climate change regulations could have on its business.
Exxon denies wrongdoing and has accused the New York and Massachusetts attorneys general, both Democrats, of pursuing the cases for political reasons. (Reporting by Nate Raymond in Boston Editing by Chris Reese and David Gregorio)