Stirling Ackroyd said since November 2015, on average, a home in London has become 33,200 euro cheaper, equating to a saving of around £26,000 for a foreign buyer.
If the country votes for Brexit this week, the value of sterling is expected to fall further – which could encourage further foreign investment in the London property market, its report said.
London has already been particularly attractive to overseas property investors in recent years, as it has been seen as a “safe haven” amid wider economic turmoil.
Foreign investors have also been blamed for making house prices, particularly in the capital, more unaffordable by adding to demand and helping fuel shortages of available stock.
Andrew Bridges, managing director of Stirling Ackroyd, said: “If Britain votes to leave the EU, sterling is set to fall further so, ironically, London would become even more affordable – and therefore more attractive – to overseas buyers.”