Dr Chris Townley, a landlord and a lecturer in competition law at King's College London, said the company had "messed with the wrong person" after charging him the fee for the installation of a security light at the front of his property after a tenant's request.
After questioning the amount, Dr Townley discovered that the contractors who installed it had charged £412.50 for the work - but added an extra commission for Foxtons.
He says he then quizzed Foxtons on the commission they received for other work on the home.
After what he says were initial refusals to provide information, he says the company admitted they received commissions on the majority of contractor work.
He claims this arrangement was never mentioned when he agreed to have Foxtons let out his property.
Solicitors Leigh Day are now taking on the case, alleging that a number of Foxtons charges are "hidden" and made without the fully informed consent of landlords.
Read the full ITV News article here