Prosecutors said Andrew Skelton, 43, leaked the information in response to a warning he was given after the company found out he used the mail room at Morrisons headquarters in Bradford to send out eBay packages.
The data breach cost the company more than £2 million to rectify, Bradford Crown Court heard.
Data containing information including salaries, National Insurance numbers, dates of birth and bank account details were sent to The Guardian, Trinity Mirror Newspapers and the Bradford Telegraph & Argus last year, prosecutor Katherine Robinson told a jury. It was also uploaded to data sharing websites.
Miss Robinson was opening the case against Skelton, a senior internal auditor at Morrisons at the time, who denies fraud and other offences.
She told the jury of seven women and five men how the defendant, of Water Street, Liverpool, was subjected to disciplinary action in 2013 after a package was found in the mail room in Bradford.
Miss Robinson said the initial suspicion was that the package contained controlled drugs but this was found not to be the case.
The prosecutor said Skelton told the internal investigator he had been conducting eBay deals using the HQ mail room and he was given a warning.
“He was allowed to continue with his employment,” Miss Robinson said. “The prosecution case is that as a result of that
Continued on Page 6: