Someone working for The Sunday Times called Abbey National pretending to be Gordon Brown to obtain details about the former prime minister's finances, the paper's editor has said.
John Witherow confirmed that the paper "blagged" information from the bank as part of an investigation in 2000 into the then-chancellor's purchase of a flat from a company owned by the late media baron Robert Maxwell.
The Sunday Times has argued that the story was in the public interest and that this would provide a defence to any charges brought under the Data Protection Act for accessing personal details, the Leveson Inquiry into press standards heard.
Robert Jay QC, counsel to the inquiry, asked him: "Abbey National, which held Mr Brown's mortgage for the flat, wrote to you alleging that someone had called its Bradford call centre six times pretending to be Mr Brown and was given information?"
Mr Witherow agreed: "That's right." Mr Jay went on: "Did someone on your behalf pretend to be Mr Brown to blag that information?" The editor replied: "Yes."
An article published in the paper in July last year said: "The Sunday Times is still trying to establish whether any journalist then on the paper sought to access Brown's mortgage information. Even if they had, such activities would have been legal as the story was clearly in the public interest.
"Section 55 of the 1998 Data Protection Act makes it an offence to access personal data - but also makes clear that this does not apply if 'the obtaining, disclosing or procuring was justified as being in the public interest'."
Earlier, Private Eye editor Ian Hislop rejected calls for statutory regulation of the press, saying laws were already in place to tackle abuses like phone hacking.
He told the Leveson Inquiry that the laws were not rigorously enforced because of the close relationship police and politicians had with senior media executives.
Mr Hislop defended the use of "blagging" by journalists carrying out investigations into wrongdoing and warned against introducing strict privacy laws like those found in France.