A leaked government memo, which claims SNP leader Nicola Sturgeon wants the Conservatives to win the general election, initially came from the Scotland Office, Secretary of State for Scotland Alistair Carmichael confirms to Channel 4 News.

Cabinet Secretary Sir Jeremy Heywood ordered an investigation into how the document, published in the Daily Telegraph, got into the public domain.

On Sunday, Mr Carmichael confirmed the memo came from the Scotland Office: “I understand that the memo in question did actually come from the Scotland Office, but these things circulate within government.”

Asked if the buck stops with him, Mr Carmichael added: “Of course as the Secretary of State for Scotland I am responsible for the Scotland Office, but you seem to be making some fairly substantial presumptions about the role of the Scotland office in this, that’s why we’re having a proper inquiry.”

Ms Sturgeon denies the claims.

Update 21 Oct 2015: the full interview with Mr Alistair Carmichael has been published below.