Prime minister Gordon Brown has failed to fill a dozen vacancies on the lowest rung of government in a vivid sign of MPs’ waning ambition ahead of an expected general election defeat.

Research conducted for the Financial Times shows that, after a spate of resignations, 12 cabinet ministers and secretaries of state are lacking a parliamentary private secretary. PPSs – known as ministerial “bag-carriers” – receive no extra pay on top of their MPs’ salary. Many have quit the government in recent months in protest over everything from the part-privatisation of the Royal Mail to the expansion of Heathrow.