Prince Andrew is at the centre of a growing controversy over his relationship with Kazakhstan following allegations about his business connections with the regime.

The Duke of York stands accused of having tried to broker a £885m deal, between a Greek and Swiss consortium and the Kazakhstan government, which would have seen him benefit from a £4 million commission.

Leaked emails appear to show that in April 2011, the Prince used his relationship with Kazakh oligarch Kenges Rakishev to help a Greek utility firm and a Swiss finance house bid for infrastructure contracts.

Aras Capital, from Zurich, and EYDAP, Greece’s largest water company, wanted to build water and sewage networks in two of Kazakhstan’s largest cities.

Prince Andrew would have been offered a commission fee of one per cent – or around £3.83million - for his role in the deal, a source at the water firm claimed.

The deal fell apart in late 2011 when Kazakh police opened fire on a group of striking oil workers, killing 14, and EYDAP pulled out for fear of being caught up in political turmoil.

Buckingham Palace denied that Prince Andrew had ever helped private organisations to pursue business in Kazakhstan.

The allegations that the Prince stood to benefit from the deal, made by an unnamed source to the Daily Mail, have not been verified.