Birley is the Eton-educated half-brother of former Tory MP Zac Goldsmith. He is the son of Lady Annabel Goldsmith and runs a range of Mayfair private members clubs that he inherited from his father.
He handed £15,000 for the Economists for Brexit group at the referendum in addition to the £10000 he donated to Green Leaves.
Although the Green Party officially backed remain at the referendum, the donation will be embarrassing for some of the senior Green figures who supported the Leave campaign, who included Baroness Jenny Jones and Green Leaves secretary Leslie Rowe.
This new link between Robin Birley and the Green Leaves campaign follows the announcement of an investigation into whether the official Vote Leave campaign group colluded with other Brexit groups to exceed election spending limits, which are strictly controlled.
A separate ruling from HMRC means that prominent right-wing leave campaigners including UKIP funder Arron Banks, Tory donor Lord Edmiston and disgraced former Tory treasurer Peter Cruddas could facing huge tax bills for their own Brexit donations.