A federal judge wants the IRS to explain under oath its lost emails, The Associated Press reports.

The AP says that U.S. District Judge Emmet G. Sullivan has given the IRS one month to hand in an explanation for its lost emails in writing. A federal magistrate will also determine whether emails can be recovered from other sources.

The order for an explanation under oath was made following a hearing on a lawsuit filed by Judicial Watch, a conservative advocacy group, The New York Times reports.

“In our view, there has been a cover-up that has been going on,” Judicial Watch President Tom Fitton told FoxNews.com. “The Department of Justice, the IRS, had an obligation, an absolute obligation to alert the court and alert Judicial Watch as soon as they knew when these records were supposedly lost.” 

In June, the IRS told Congress that it had lost many of ex-IRS official Lois Lerner’s emails prior to 2011 because her computer malfunctioned during the summer of that year. Lerner was responsible for the IRS division that dealt with applications for tax-exempt status. Last year, the IRS said agents had wrongly examined applications for tax-exempt status by tea party and other right-wing groups.