The chairman of the Prince of Wales’s charitable foundation has resigned, expressing concern over potential “rogue activity” after reports that the organisation accepted a six-figure sum from a Russian donor.

Charles wrote a letter thanking the businessman for his generous offer of more than £500,000 to the Prince’s Foundation last year, and suggested they could meet after the Covid crisis.

The Scottish Charity Regulator launched an investigation into the matter earlier this week.

The charity initially received £100,000 but the total sum was reportedly rejected by the ethics committee of the foundation, which has its headquarters in Scotland, following concerns about its provenance, according to the Sunday Times.

On Wednesday, chairman Douglas Connell, who has been in the role since March, said he should accept responsibility “if it appears that serious misconduct may have taken place”.

HeraldScotland:

Former royal valet Michael Fawcett temporarily stepped down as chief executive of the Prince’s Foundation after an alleged cash-for-honours scandal (Chris Young/PA)

Mr Connell said in a statement: “I am both shocked and dismayed by newspaper reports that rogue activity of various kinds may have taken place within and outside the Prince’s Foundation.

“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.”

The investigation launched by the Scottish Charity Regulator comes shortly after an alleged cash-for-honours scandal which saw Michael Fawcett temporarily step down as the foundation’s chief executive earlier this month.

Last week, Clarence House said the prince had “no knowledge” of the issue after Charles and Mr Fawcett, one of his most trusted confidants, were reported to police over the claims.

Pressure group Republic contacted Scotland Yard and reported both the future king and Mr Fawcett, Charles’s former royal valet, on suspicion of breaching the Honours (Prevention of Abuses) Act 1925.

The chief executive is accused of promising to help secure a knighthood and British citizenship for a Saudi billionaire donor.

READ MORE: £100,000 donation to Prince Charles' foundation probed by Scottish Charity Regulator

Charles is president of the foundation but not involved with its governance, with the charity’s trustees overseeing its day-to-day activities.

An investigation has been launched into the allegations relating to Mr Fawcett by an independent team on behalf of the foundation’s trustees.

A Clarence House spokesman said of that probe: “The Prince of Wales fully supports the investigation now under way at the foundation.”