The money was repaid in 2009 and was followed by a reported further £1m donation in 2011.
He became the party's chairman of nations and regions and volunteered to raise support and money around the country.
In the past Mr Rosenfeld had also supported the Conservatives, giving £10,000 to Ken Clarke's party leadership campaign in 2001.
The multi-millionaire returned to Britain around two years ago after spending five years in Switzerland.
He made an estimated £100m through a property investment company, Minerva. He sold the firm in 2006 and moved his family to Geneva.