Mr Brown was defiant in the face of City outrage despite the UK government’s annual operating loss of £100bn, rising to £1.5 trillion when the write-down of its banking assets is taken into account.

The prime minister said: “I’ve been building up this pension since I became an MP, it’s all completely legal and now you want to take it away because I’ve been catastrophically bad at my job and you’re looking for a scapegoat. What gives?”

He added: “Yes I’ve been in charge of financial regulation for 12 years, yes I encouraged the housing bubble, and yes I pissed billions up the wall giving pointless jobs to Labour voters, but I fail to see what any of this has to do with me being incredibly well off.”

Brown’s £3m pension pot is expected to cast the spotlight on the extravagant retirement packages of other failed politicians including Alistair Darling’s inexplicable £1.7m and the £1.5m awarded to John Prescott for being a national disgrace for 10 years.

Meanwhile Margaret Beckett has a fund worth £1.7m, and Tessa Jowell has £1m even though no-one has the faintest idea what either of these actually do.

Critics insist Mr Brown has a moral duty to hand back his pension fund as he will inevitably receive a multi-million pound advance for two volumes of eye-gougingly tedious memoirs which will end up in the bargain bucket at WH Smith within a fortnight.

Martin Bishop, head of pension rows at the Institute for Studies, said: “It’s a fascinating dynamic. The politicians blame the bankers, the bankers blame the politicians, and the ordinary taxpayer is down on all fours with a confused look on his face, being fucked at both ends.”