Gordon Brown wrote a dying Mo Mowlam two “emotional” letters expressing his sadness over her terminal illness and his profound remorse over the disintegration of her cabinet career under Tony Blair.
The Prime Minister sought to heal a long-standing rift with his former cabinet colleague shortly before she died in 2005 from a malignant brain tumour.
Mr Brown, who was then Chancellor of the Exchequer, wrote to the former Northern Ireland Secretary and her husband, Jon Norton, expressing his sadness at her condition.
But it is understood that he also expressed his regret about the coldness that had afflicted their relationship for more than 15 years.
One source with intimate knowledge of the letters, sent within days of each other in the summer of 2005, said each ran into several pages and had “the ring of sincerity” about it.
He added: “Gordon said he was deeply sorry about Mo's condition, but he went much further.
“He said she could have achieved so much more if circumstances had not conspired against her.”
Details of Mr Brown's attempt to bury the hatchet came as a TV drama last night revived memories of Mowlam's frustrations at the politics that helped to force her out of the Cabinet.