The Conservative trade and industry spokesman Crispin Blunt quit his post as voting ended on 1 May, but before they were counted. Here is his full resignation statement.
"This evening I resigned from Iain Duncan Smith's frontbench team as I can no longer reconcile my public duty to him with my own views of the consequences of his leadership for the success of the Conservative Party.
"Whatever the headline results in today's local elections the fact is the Conservative Party is making no real progress when we should be taking advantage of the opportunity our opponents and events have offered.
"If the electorate perceived us as a credible alternative government the potential support for us could carry us back to government.
"However we carry the handicap of a leader whom Conservatives in Parliament and outside feel unable to present to the electorate as a credible alternative Prime Minister.
"When he was elected, Iain emphasised the importance of the image he would present in his first three months.
"He made little impact, but at the time many thought this was an aberration due to the events of 11 September 2001.
"However Iain's analysis has turned out to be entirely accurate. He has failed to make the necessary impact on the electorate and I don't see any prospect of him doing so.
"The consequences of how we come across are something we have to accept as professional politicians.
"If we were a business being operated in the interests of its shareholders or a football club in the interests of its supporters, the managing director or manager would by now have been replaced.
"If we are a political party that is serious about regaining power, our leader has to now be replaced.
"I hoped the leader could recognise this analysis himself. The policy work he has initiated reflects credit on him and if he were able to accept the enormous personal sacrifice required by the wider interests of the party he would show himself to be an individual of rare quality.
"Iain was not prepared to entertain this. My alternative suggestion was that he should initiate a vote of confidence from the parliamentary party. If he commanded our confidence, his and therefore our position would be improved.
"It would also recognise an event that many regard as inevitable, but give him the initiative rather than his Parliamentary colleagues. He did not accept this suggestion.
"If the leader cannot recognise what the wider interests of the party require, our constitution places the responsibility upon the parliamentary party. My conclusion is that our urgent duty to the wider Conservative interest is to face up to this unpleasant responsibility now.
"In my judgment any of the likely successors to Iain Duncan Smith can be credibly presented to the electorate as the alternative prime minister. One of the reasons I feel able to address this issue publicly is that I am not associated with any of the likely candidates.
"If we are decisive now we can put our party back on the route to government under a new leader or at the very least give Iain the vote of confidence that will resolve the issue formally for a year, but in practice until the next general election. Either way I believe our position will be improved.
"If we fail to act we will only have ourselves to blame for our party's and country's continued misfortune."