Donald Trump faces renewed scrutiny of the riches that flowed into his real estate empire from the former Soviet Union after a fixer for a Kazakh family accused of pumping dirty money into US property agreed to assist an international investigation into his former business partners.

Felix Sater, a Russia-born dealmaker with organised-crime connections who worked on ventures including Trump Soho in Manhattan, has attracted attention in recent months as efforts continue to chart the links between the US president’s circle and moneymen from Russia and its neighbours.

In October the Financial Times revealed that Mr Sater had helped the family of Viktor Khrapunov, a former Kazakh minister now exiled in Switzerland, invest millions in US property through front companies. The Khrapunovs have spent heavily across the US, including, records indicate, buying apartments in Trump Soho.