Olly Robbins refused to hand Peter Mandelson’s vetting summary to the Cabinet Office, the civil servant who leads the department has said. The summary – which would have revealed that Robbins, the now-sacked Foreign Office head, had granted Mandelson clearance against the advice of security officials – was instead provided to Cat Little by UK Security Vetting, she said.

Giving evidence to the Commons foreign affairs committee, Little, the permanent secretary at the Cabinet Office, disputed the claim by Robbins that her department had suggest Mandelson might not need vetting at all. Citing “a number of emails” that she had reviewed, she said it had actually been the Foreign Office that raised the possibility of Mandelson not needing to be vetted given he was a member of the House of Lords.

Questioned by Emily Thornberry, the committee chair, Little confirmed evidence from Robbins on Tuesday that there had been internal debate about whether to release vetting documents about Mandelson to the Cabinet Office. Little’s department has been gathering documents connected to Mandelson’s appointment as the UK’s ambassador to the US, in response to a Commons “humble address” motion forcing their release.

As part of this, she told the committee, Robbins – who was dismissed as Foreign Office permanent secretary after it emerged that Downing Street was not told Mandelson was initially refused security clearance – resisted her department seeing vetting documents. There was, she explained, “lots of debate and discussion about how to treat vetting information”, which included a meeting in mid-March with Robbins and his team, after being told about the existence of a summary as to why Mandelson was refused vetting.

“I specifically asked to see this document in any decision-making audit trail around those judgments,” she said. “At the time, it was made clear to me that that information would not be forthcoming.” In response, Little said, she “took the very unusual judgement” to go directly to UK Security Vetting, the vetting department that sits within the Cabinet Office, so she would be able to comply with the Commons motion to provide all the information about Mandelson.