Nick Clegg said he would refuse to lead the Liberal Democrats into a power-sharing deal without radical constitutional reform as he sought to portray himself on Sunday as a Westminster outsider fighting to “prise open the rotten old system”.

In his first party conference speech as leader, Mr Clegg also signalled his openness to proposing tax cuts – a surprise move that could outflank Labour and the Conservatives by breaking the political consensus on levels of public spending.