Deputy Governor of the Bank of England (BoE) Paul Tucker is to be questioned by MPs when he appears before the Treasury select committee.
Tucker is expected to be grilled over conversations he had with former Barclays chief executive Bob Diamond in the wake of the Libor rigging scandal.
He is viewed as likely to succeed Mervyn King as governor of the BoE when King steps down.
Diamond revealed that Tucker spoke to him about Libor in 2008, but maintained he did not give any instructions to manipulate the bank rates.
In an internal memo, Diamond wrote that Tucker received calls from "senior figures in Whitehall" who were concerned about the bank's high Libor.
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"I didn't believe it was an instruction," Diamond told MPs during his appearance before the Treasury Select Committee on 4 July.
The subsequent fall in the bank's Libor interest rate might have been due to Jerry del Missier, chief operating officer at the time, having misinterpreted the message as an instruction by the BoE to keep the Libor low, Diamond added.
Barclays was fined £290m by the UK and US regulators for manipulating the Libor. During his appearance before the committee, Diamond said Barclays was not the only bank to engage in such practices.
Three of Britain's biggest banks - Royal Bank of Scotland (RBS), Lloyds and HSBC - are among 17 banks being investigated by regulators for rate fixing.
Labour leader Ed Miliband is expected to deliver a speech on his vision for the banking sector after previously demanding that errant bankers face strict prison sentences.
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