A federal judge in the United States has ordered the Department of Justice to stop threatening state and local election officials with criminal prosecution over their handling of ballots ahead of the November 3 midterm elections.

The temporary restraining order was issued on Friday by Judge Trina Thompson of the Northern District of California following a lawsuit filed by labour unions and civil rights organisations against the Justice Department and the Department of Homeland Security.

The ruling prevents federal officials from pressuring election workers to stop processing ballots belonging to registered voters solely because the government questions their eligibility.

It also bars the Justice Department from threatening election officials with prosecution for refusing to follow such instructions.

The case is linked to efforts by the Trump administration to restrict voting by individuals suspected of not being US citizens.

In her ruling, Thompson said the plaintiffs had shown that they were likely to succeed in their legal challenge, adding that the approaching election made immediate intervention necessary. The order is expected to remain in force until November 16.

The judge also prohibited federal authorities from demanding that specific registered voters be removed from electoral lists, denied ballots or have their votes excluded based on claims of ineligibility.

The decision follows another setback for the Justice Department on Wednesday, when a federal judge rejected its attempt to invalidate the ballots of more than 20,000 California voters whose citizenship status had been questioned.

The development comes as President Donald Trump’s Republican Party faces the possibility of losing its control of Congress in the midterm elections.

Trump has repeatedly raised concerns about alleged electoral fraud, although studies have found that voter fraud cases in the United States are rare and have not significantly affected election outcomes.