WASHINGTON - A whistleblower complaint says that Elon Musk's team of technologists may have been responsible for a "significant cybersecurity breach," likely of sensitive case files, at America's federal labour watchdog.

The complaint, addressed to Republican Senate Intelligence Committee chairman Tom Cotton and his Democratic counterpart, Mr Mark Warner, and made public on April 15 by the group Whistleblower Aid, draws on the testimony of Mr Daniel Berulis, an information technology staffer at the National Labour Relations Board (NLRB).

The NLRB, a New Deal-era agency that is tasked with protecting workers' rights to organise and join unions, has for years been a target of America's corporate titans, including Mr Musk, some of whom are now seeking to have the agency's powers declared unconstitutional.

In an affidavit, Mr Berulis said he had evidence that Doge staffers were given extraordinarily sweeping access to the NLRB's systems, including to sensitive case files.

He said that beginning in early March, logging protocols created to audit users appeared to have been tampered with, and that he had detected the removal of about 10 gigabytes worth of data from NLRB's network sometime thereafter.

"That kind of spike is extremely unusual because data almost never directly leaves NLRB's databases," Mr Berulis said in his affidavit.

A spokesperson for Mr Musk's team - officially known as US Doge Service - did not immediately reply to a message seeking comment.

A message left with the NLRB also was not immediately replied to, although NPR - which first reported the story - quoted an NLRB spokesperson as disputing Mr Berulis' claims and saying there had been no breach.

Mr Cotton and Mr Warner did not immediately reply to messages seeking comment.

NPR, which said it interviewed 30 sources in government, law enforcement, the cybersecurity industry, and the labour movement about the complaint, said that the disabling of logging software was reminiscent of cybercriminal behaviour.

Mr Berulis' affidavit said that an effort by him and his colleague...