Jeremy Corbyn has had his "Right Honourable" title removed from the Commons website on the orders of the Queen's advisers, after No 10 wrongly implied the Labour leader had joined the Privy Council.
The Labour leader had been accorded the title ahead of his appointment to the Privy Council.
However, after he missed the first meeting of the Privy Council since the summer holidays with the Queen last Thursday, the "Rt Hon" title was removed from Mr Corbyn's page on Parliament's website.
This was done under the orders of the Office of the Privy Council, The Daily Telegraph reports.
Mr Corbyn missed an induction into the Privy Council by the Queen because he was on a walking holiday in the Scottish Highlands at the time.
He cannot become a member of the Privy Council until the next meeting is held, probably next month.
This will mean the Labour leader cannot be briefed on security matters until then, complicating efforts by ministers to use intelligence to persuade Mr Corbyn to back British involvement in military action in Syria.
David Rogers, a leading expert on the Privy Council, told the Telegraph the confusion was caused by a statement on the Cabinet Office's website that said Mr Corbyn had been appointed to the Council.
The statement read: "The Queen has been pleased to approve the appointment of Jeremy Corbyn MP as a member of the Privy Council."
Mr Rogers said:" Number 10 had confused a recommendation to appoint with an actual appointment" and added that Downing Street "probably hadn't cleared their statements with the Privy Council Office".
He said the Privy Council had stepped in to ask Parliament to correct its website and remove Mr Corbyn's title.
The Labour leader will have to send a Privy Counsellor in his shadow Cabinet team for briefings, such as any on British involvement in Syria.
The Privy Council's monthly meetings are presided over by the Queen, but its role as an administrative link between the monarch and parliament is institutional, rather than politically critical.
David Cameron was named as a member of the Privy Council eight days after he was made Conservative leader.
He did not attend a Privy Council meeting and was therefore not sworn in for a further three months, but unlike Mr Corbyn he was appointed in his absence.
A spokesperson for Jeremy Corbyn said he intended to take up the position on the Privy Council.
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