LONDON (AP) — A British government minister resigned Saturday amid a crisis over alleged bullying within the governing Conservative Party sparked by the death of a young activist.

International Development Minister Grant Shapps sent a resignation letter to Prime Minister David Cameron, saying "the buck should stop with me."

Shapps was party chairman until May's general election, and has been accused of failing to act on claims of bullying and abusive behavior in the Conservatives' youth wing.

Conservative activist Eliott Johnson, who was 21, was found dead on railway tracks in September in an apparent suicide. He had accused Conservative youth organizer Mark Clarke of bullying.

Clarke denies wrongdoing but was expelled from the party as it emerged that other Conservatives had also accused him of bullying, sexual harassment and blackmail.

The party had previously said it was not aware of any other allegations against Clarke, who ran an operation that sent young activists to campaign in close-fought constituencies during the election.

In his resignation letter, Shapps said that "although neither the party nor I can find any record of written allegations of bullying, sexual abuse or blackmail made to the chairman's office prior to the election, I cannot help but feel that the steady stream of those who raised smaller, more nuanced, objections should have perhaps set alarm bells ringing sooner."

Cameron said Saturday that Johnson's death was "a tragic loss of a talented young life" and said there would be a full party inquiry overseen by an independent lawyer.