In an outspoken interview, Jack Straw said he regularly considered challenging Mr Brown for the top Labour role but was “afraid to strike”.
The former Justice Secretary ended up running Mr Brown’s leadership campaign even though he knew his colleague was not trusted and did not understand how to unite a team.
“The tragedy was that we realised, but so did Gordon, that this job – for which he’d become obsessed and devoted his life – was a job that he couldn’t properly do,” Mr Straw told BBC Radio 3’s Night Waves. “He just lacked the fundamental qualities to do it.”
Mr Straw, who was previously Home Secretary and Foreign Secretary under Tony Blair, believes he would himself have made a good prime minister but he did not “want it enough”.