A proposed class-action lawsuit accusing Fitbit of misrepresenting the ability of its wearable fitness products to track sleep can move forward, a federal judge has ruled.

The San Francisco federal lawsuit claims that Fitbit materially misrepresented on its packaging the ability of the Flex product to track users' hours slept, times woken up, and sleep quality. The suit alleges false advertising, unfair trade practices, fraud, and a host of other claims.

US District Judge James Donato did not rule on the merits of the case but instead refused to toss the lawsuit as Fitbit had wanted. Now Fitbit, which claimed the allegations were based on "bad science," according to the judge, must mount another defense to the allegations. The case could still be dismissed at a later stage, and it might also go to a trial or settle.

"Fitbit’s dismissal request is focused on attacking the plaintiffs’ evidence as bad science and proffering a compilation of studies that it believes validates the efficacy of accelerometer-based sleep tracking," the judge wrote. "Fitbit disputes those allegations and the parties clearly have sharply divergent views about sleep monitoring technology and what works and what does not, but those issues of fact are far beyond the scope of this motion to dismiss. And even if Fitbit’s studies might validate the use of accelerometers for sleep monitoring, plaintiffs’ claims arise out of Fitbit’s representations on product packaging and similar sources. Consumers are not expected to do research 'beyond misleading representations on the front of the box.'"

Fitbit said in a statement that it would "vigorously" defend the case, which it said has "no merit."

The lawsuit, (PDF) which was filed last year and amended, cites a 2012 study in the journal Sleep Health as evidence that the Fitbit allegedly does not adequately track sleep.

The judge gave Fitbit until July 29 to respond to his Friday ruling.