Joy Johnson, who left her post in January, said the differences between the two were well known. "There are obviously differences. It is quite obvious. We read about it. We know there are differences," she told BBC Radio 4's The World at One programme.
Attention had been drawn to the ill-feeling between Mr Brown and Mr Mandelson, which dates back two years to the Labour leadership election after the death of John Smith, by a report in the Times.
The article prompted fierce recriminations in Westminster yesterday. A Brown loyalist yesterday suggested Mr Mandelson was in some way responsible, and contrasted Mr Brown's standing as shadow chancellor with that of Mr Mandelson, "the new MP for Hartlepool".
Ms Johnson was seen as close to the shadow chancellor's team and clashed with Mr Mandelson after she was recruited from the BBC to oversee the party's campaigns, elections and media operation.
Party officials yesterday sought to play down suggestions that Mr Brown and Mr Mandelson were not on speaking terms, saying that they met several times a week - most importantly at the daily planning meeting in Mr Brown's office every morning - and occupy virtually adjacent offices.
Ms Johnson accepted that reports were damaging for the party. "These sorts of stories are not good for the party. They know that. They are working for ending 17 years of Tory rule and, at the end of the day, they want a Labour government . . ."Reuse content