David Cameron's response to Iain Duncan Smith's resignation letter in full

. Credit: Andrew Matthews/P

Prime Minister David Cameron has responded to the resignation of work and pensions secretary Iain Duncan Smith this evening by saying he was "puzzled and disappointed" by his decision to quit.

Duncan Smith stepped down from his post claiming it was because of Treasury pressure to make cuts to benefits but Cameron responded to the work and pensions resignation reason by suggesting the proposed cuts had been "collectively agreed".

Since the resignation on Friday night Downing Street has told ITV's Political Editor Robert Peston that the current version of proposed disability cuts will be dropped but indicated cuts may still go ahead in a a different form.

David Cameron's full letter of response to Iain Duncan Smith's resignation: