Billed by the elite club's panel as "the brains behind New Labour," it is Mr Mandelson who finishes well ahead of his parliamentary rivals. He scores an impressive 90 PQ points out of a possible 100.
The Trade Secretary may "not be universally liked" by his colleagues in the Labour Party, but he is considered an astute operator, without being seen as a "pointy head" (the term said to be used by Gordon Brown's spin doctor Charlie Whelan to disparage intellectuals).
Mr Mandelson is closely followed by Stephen Byers, the Chief Secretary to the Treasury, on 85 points, and Jack Straw, the Home Secretary, on 75.
Others are not so highly valued. Clare Short, Secretary of State for International Development, was downgraded for having "a mouth that is bigger than her brain." She earned only 30 PQ points and came joint bottom with Nick Brown, the new Minister of Agriculture.
Jack Cunningham, Chancellor of the Duchy of Lancaster, and Robin Cook, the Foreign Secretary, only just managed to beat them with scores of 35.
The PQ league table, published today in Mensa Magazine, was drawn up during secret deliberations by an anonymous jury of Mensans, each of whom had an IQ of over 148. The 12 panellists included several captains of industry and leading civil servants.
The jury set out to assess each Cabinet member purely on political performance rather than on their basic level of intelligence. "Our jury took the view that some of the Cabinet were too clever by half," said Simon Clark, editor of Mensa Magazine.
"It was not as scientific as an IQ allocation, but we asked each member to rate the politician on ability and then on intellectual ability."
Mensa acknowledges that, while an individual's IQ rating will remain static throughout their life, there is scope for improving a PQ score. "Robin Cook did not do that well this time, but it is possible that next year he will score more than 35."
Noel Burger, Mensa chairman, said his panel had been correct to assume that a powerful intellect was not the same thing as a good political brain.Reuse content