Byrne, a former Labour Party chief press officer with strong links to Lord Mandelson, lashed out on Twitter this morning.
He said: ‘What the hell is a strike mongering politically discredited nutter like Charlie Whelan doing at the heart of Labour's election campaign?'
Whelan stepped down as a special adviser to Gordon Brown, then chancellor, in 1999 amid claims that he had leaked sensitive information about Mandelson which led his resignation from the Cabinet.
Since then Whelan has been political director of the Unite union, but has remained close to Brown and is now reported to be set for a key role in Labour HQ during the election campaign. Although Downing Street has denied that he is returning in an official capacity, Whelan is already believed to be working closely with Douglas Alexander, Labour's general election co-ordinator.
Political commentators have recently hinted at disquiet in the Labour ranks over the return of Whelan. But until today Labour figures have refrained from public criticism of the controversial former spin doctor.
Although Byrne has not had a formal Labour role for some time, he was the Labour Party's chief press officer from 1988 to 1996, working closely with then communications director Mandelson, and also sharing a flat for three years.
Byrne joined Shandwick Consultants in 1996 and was made European CEO of Weber Shandwick UK and Ireland in 2009.
Whelan told PRWeek he was not aware of the Weber Shandwick boss. Asked for a response to Byrne's comment, he said only: ‘Who he?'