The charity's executive director Chris Martin has temporarily stepped aside pending the outcome of the investigation into the claims, it has been revealed. This comes just hours after Douglas Connell, the chairman of the Prince’s Foundation, quit.

       Express.co.uk has approached Clarence House for comment following these new resignations.

       Upon stepping down, Mr Connell said to be "shocked and dismayed" by reports "rogue activity of various kinds" may have taken place at the charity.

       He added: "I and the other members of the board of trustees had no knowledge of any such activity and we have launched a rigorous and independent investigation.

       "My view is that the person chairing any organisation should take responsibility if it appears that serious misconduct may have taken place within it.

       "I believe that the correct course of action is for the chair to accept that responsibility and to stand down from the role.

       "That is why I am today resigning as chair of the Prince’s Foundation."

       Mr Connell's resignation came a few days after the Scottish charity regulator (OSCR) launched a probe into claims a Russian banker, Dmitry Leus, believed to have donated ￡500,000 in two installations to the Foundation in May through third-party fixers.

       However, he reportedly later discovered only ￡100,000 had been received by the charity.

       The donation was intended to go to Dumfries House, an 18th-century estate part of the Foundation.

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       The charity had reportedly initially received ￡100,000 but its ethics committee later rejected the donation after discovering Mr Leus had been found guilty of money laundering in Russia in 2004 before having the conviction overturned.

       There is no suggestion of any wrongdoing by Mr Leus.

       In May, Prince Charles wrote a "thank you" note to the banker saying to be "incredibly grateful" for his "immense generosity".

       The OSCR is also looking into claims Michael Fawcett, one of the Prince of Wales's closest aides and chief executive of his foundation had offered to help secure a knighthood and British citizenship for a billionaire Saudi donor, Mahfouz Marei Mubarak bin Mahfouz.

       A spokesman for the regulator said: "We have been working with the Prince’s Foundation to better understand the use of the organisation’s funds, and to gain a full understanding of the work which is being undertaken by the charity’s trustees to investigate the range of issues which have been raised in the media."

       The cash for honour claims are being investigated also by the ethics committee within the Prince's Foundation, as it was announced in late August.

       Following Mr Connell's resignation, a spokesperson for the Prince's Foundation said it respected and understood his decision to step down.

       They told Express.co.uk: "The Prince’s Foundation understands and respects Mr Connell’s decision to step down.

       "We would like to thank him for all his work to date and wish him well.

       "Dame Sue Bruce, Vice Chair, will take on the role of Acting Chair with immediate effect.

       "The Prince's Foundation takes very seriously the allegations made in recent news articles and is committed to the highest ethical standards.

       "These changes to the board of Trustees will not impact the scope or timing of the rigorous independent investigation already underway."

       Mr Fawcett was the first prominent figure at the Foundation to temporarily resign in the wake of the allegations.

       Clarence House said after claims regarding the citizenship and the honours for the Saudi businessman emerged: "The Prince of Wales has no knowledge of the alleged offer of honours or British citizenship on the basis of donation to his charities and fully supports the investigation now underway by The Prince's Foundation."

       The Prince's Foundation was created through a merger in 2018 of a series of pre-existing charities founded by Charles.

       It is a charity aiming at creating harmonious communities through education, practice and places.

       Every year, it delivers education and training programmes benefitting more than 15,000 pupils around the world.