Nick Timothy, May's co-chief of staff, said on the ConservativeHome website that he stepped down on Friday, while the BBC reported that Fiona Hill had also quit.
"The reason for the disappointing result was not the absence of support for Theresa May and the Conservatives but an unexpected surge in support for Labour," Timothy wrote."I take responsibility for my part in this election campaign, which was the oversight of our policy program. In particular, I regret the decision not to include in the manifesto a ceiling as well as a floor in our proposal to help meet the increasing cost of social care," he added.