Washington (CNN) A federal judge told US House and Senate Democrats they can begin collecting financial evidence this week about Donald Trump's businesses for a lawsuit.

Judge Emmet Sullivan, of the US District Court in Washington, denied an attempt by the Justice Department to stop the Democrats from collecting information from the Trump Organization and to appeal early court decisions in the lawsuit, which tests the constitutionality of Trump's business holdings while he serves as President.

The case is one of several avenues Democrats have to get to Trump's financial records.

Sullivan said the group of more than 200 members can begin collecting evidence June 28 through late September. Previously, the members of Congress said they plan to seek both documents and depositions from the Trump Organization.

But the Justice Department had hoped to take the case to an appeals court before the evidence collection began.

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