Iain Duncan Smith's choice for chief executive of the Conservative Party is facing damaging allegations that he considered defecting to the UK Independence Party.

Senior Tories revealed that former MP Barry Legg allegedly approached the head of the UKIP before the last election to discuss the possibility of switching allegiances.

Michael Portillo has waded into the row, accusing Duncan Smith of damaging the party with provocative personnel changes.

In his first criticism of the Tory leader since his defeat in the 2001 leadership contest, Portillo told today's Telegraph: "My constituents are dismayed at another round of infighting which appears to have come from a clear blue sky and to be causing damage which is purely self inflicted."

Central Office attempted to play down the row, saying that "no one is slightly interested" in internal party matters.