Mr Whelan stepped down in January after he was blamed for leaking details of Geoffrey Robinson's pounds 373,000 loan to Peter Mandelson but he helped the Chancellor with the campaign for the Scottish Assembly elections last month.
Mr Brown's new right-hand man, Ian Austin, 34, was the deputy director of communications for the Scottish Labour Party during that same campaign. He was previously Labour's West Midlands regional press officer until his secondment to Scotland last year.
Mr Austin, who will take up his post later this month, will work closely with existing special advisers and the Treasury press office.
Mr Whelan was known to take personal charge of all Mr Brown's media affairs.
The Treasury said Mr Austin would work with the head of communications, John Kingman, who remains Mr Brown's "principal spokesman" on economic and policy issues, the Treasury said. The Chancellor's press officer, Fiona Hamilton, will continue to have day to day responsibility for Mr Brown's media appearances.
The Tories have also tried to boost their public profile by appointing Andrew Scadding as their assistant head of media. Mr Scadding, 34, is a senior producer of the BBC's political programme On The Record and has worked on the corporation's coverage of party conferences and elections.
Mr Scadding's appointment follows that of Amanda Platell, a former editor of The Sunday Express, as the party's head of media in April. He will take up his post next month.