NICK Clegg risked opening himself up to being the butt of a string of political jokes yesterday when he suggested he had been "gradually lobotomised" by his time at the head of the Coalition Government.

The Deputy PM blamed the "sheer neurosis and weight" of the relentless Whitehall machine for his supposed condition, claiming the pressures of modern politics left MPs unable to see the big picture.

In a speech to Liberal think-tank Centreforum, Mr Clegg explained: "You stop thinking a bit. You stop looking into the middle horizon. Instead your nose is pressed up against the window pane of everyday activity. But if there ever was a time that we need to think big, it is now."

The LibDem leader said this feeling of pressure was something generations of politicians had experienced but noted how the present time was unusually busy and uncertain.

"It would be pretty difficult, since the ... 1970s, to think of a time that social, political, economic convulsions have taken place on the scale and in such an unpredictable way as it is now," he added.

Mr Clegg's joke about being lobotomised did not, apparently, go down well with one member of the audience. Lord Steel, the former Liberal leader, was said to have rolled his eyes when the Deputy PM spoke of having his brain removed.