John Sentamu is expected to get a life peerage imminently, it has emerged, after the Government was accused of "institutional prejudice" over Britain's first black archbishop not being automatically ennobled.

It was expected that Mr Sentamu, 71, who retired as the Archbishop of York on June 7, would be given a life peerage so he could continue sitting in the House of Lords in a personal capacity.

But No 10 did not announce the peerage despite his predecessor Lord Hope and the former Archbishops of Canterbury Rowan Williams and George Carey being made life peers when they stepped down.

A backlash was in part fuelled by a No 10 spokesman telling the Sunday Times that Mr Sentamu was kept off the list to keep numbers in the House of Lords down, despite Prime Minister Boris Johnson including his own brother, Jo Johnson.

However, a Whitehall source later told the PA news agency that Mr Sentamu's peerage was "imminent" and that the delay was due to a procedural hold up with the House of Lords Appointments Commission.

"He was put forward for a peerage but the approval process is still ongoing," the source said.

As an archbishop, he was among the 26 lords spiritual who have their places reserved in the upper chamber of Parliament for Church of England bishops.

After he stepped down, Mr Sentamu was informed by No 10 that he was in line for a peerage, asking him to confirm his suitability and willingness to accept, the Sunday Times reported.

However, a month later he was told that his name would not be included.

His successor, Stephen Cottrell, who was enthroned as the 98th Archbishop of York on Sunday, tweeted: "Disturbed to find out today that whether it be through negligence or intent my predecessor + Sentamu has not been given the peerage that has been the custom for many years.

"I trust this will soon be rectified. UKHouseofLords will benefit from his voice."

David Lammy, the shadow justice minister, said on Twitter : "No 10 broke a precedent and snubbed Britain's first black archbishop for a peerage because it says the House of Lords is too large, but it made room for Ian Botham, Claire Fox and Theresa May's husband. Blatant institutional prejudice."

David Davis, the former Conservative cabinet minister, said: "Number 10 has made a mistake in not ennobling John Sentamu.

"He was a great archbishop. It cannot claim it needs to limit the size of the Lords whilst elevating Boris's brother. It should be put right immediately."