Emails exchanged between Jeremy Heywood, a senior civil servant in the Cabinet Office, and the Bank of England's Executive Director for Markets Paul Tucker have been released to the press.
The emails were released to John Mann, MP for Bassetlaw, after he made a Freedom of Information request for "all copies of emails and transcripts of telephone conversations between Deputy Governor, Paul Tucker and Bob Diamond between 1 October 2008 and the 30 November 2008".
Mr Mann has said he intends to warn the Bank of England that it may be in contempt of Parliament because it did not release the documents before Bob Diamond's appointment with the Treasury Select Committee.
In the emails, Mr Heywood raises his concern that Barclays was trading above the Libor rate.
Bob Diamond tonight angrily rejected suggestions that he misled MPs over regulators' concerns about activities at Barclays.
The Bank of England's Paul Tucker told MPs he refuted claims that he attempted to influence Barclays into manipulating the Libor rate.
MPs will be hoping the Deputy Governor of the Bank of England will shed some light on unanswered questions about rate-fixing at Barclays.