A new class action is being assembled against Foxtons over its charging of fees to tenants.

The case has major implications for all letting agents in England that levy tenancy fees.

If the action is won, it could mean letting agents having to refund fees charged in the last six years.

It is being actively promoted on social media by the law firm CaseHub, which says it “brings justice to people by building group legal battles, online. Join our class actions against Ryanair, letting agents and Parking Eye.”

In one tweet, it says: “Ever paid tenancy fees in England. Sign up for updates on upcoming case against letting agents. U could get refunded.”

Michael Green, founder of CaseHub, says that letting agent fees could be illegal under the Unfair Terms in Consumer Contracts Regulations 1999, and its successor the 2015 Consumer Rights Act.

Foxtons charges include £420 for administration, but Green says the true cost is around £55.

If the claim is successful, Green says it will not be just tenants of Foxtons who will benefit, but millions of other tenants of other agents who, he believes, could be repaid some £2bn.

He believes the lawsuit could cost Foxtons itself some £80m.

In an interview with the Guardian, Green claimed that most letting agents avoid mentioning fees until the last minute, quote prices without VAT and profit from their fees rather than simply covering their costs.

He said: “We have ended up with the ridiculous situation whereby tenants are paying hundreds of pounds for a five-minute template contract, or for a credit check which is available on the market for £20.”

He said the action is being brought against Foxtons because its practices are illustrative of the rest of the market.

He said: “If we win a case against Foxtons, it opens up liability against most other agents. They won’t like that.”

Green, 25, will pick up around one-third of the pay-outs that he might win for those who sign up.

So far, he has signed up over 5,000 people to a £400m suit against Ryanair, and says he will need to sign up 1,000 for the Foxtons case.

Yesterday, Foxtons told EYE: “Foxtons employs an open and transparent approach when it comes to fees.

“Our tenancy administration fees are fixed and charged per tenancy (not per individual tenant) and includes the cost of chauffeured viewings, negotiating the tenancy, verifying identification, obtaining references and drawing up the tenancy agreement.

“We ensure tenants have full visibility of fees upfront before making any important decisions, by displaying our fees on our website, on print and digital advertising, within branches and on all the pre-tenancy paperwork.

“Unfortunately this practice is not always replicated by other agents, and we welcome more regulations to improve transparency in the industry.”

Foxtons is already facing the possibility of another class action battle, which again could have implications for other letting agents;

This is a potential lawsuit being brought on mark-ups charged to landlords by building and maintenance, and other, contractors. The law firm in that case is Leigh Day which says that if successful, it could cost Foxtons millions. The case was announced last year.

At the end of February, Leigh Day announced that 55 landlords had joined the class action and were claiming a total of £2.14m in what they say are “overcharges”. It is threatening to take their claim to the High Court.

Foxtons has said of that case that it “reflects a small minority of landlords and we believe is entirely without merit”.