Today is the first anniversary of OnTheMarket which Russell Quirk has marked by hitting out at the challenger portal.

He claims that agents are pouring their money into a financial black hole and that their support of it is proving “shockingly expensive”.

But last night, a spokesperson for OTM said: “If Mr Quirk is so adamant that OnTheMarket is set to fail, why is he so exercised about it?

“Naturally Mr Quirk is entitled to his opinion.

“Our 3,000-plus estate and letting agent member firms are also entitled to theirs and understand better than anyone their long-term objectives in supporting OTM.

“Nobody should under-estimate the strength of resolve amongst our members to regain control of their data and their costs and to create a genuine alternative to the current market leaders, which serves both consumers and agents better.

“Indeed, we recently announced that overall support, including firms who have signed Letters of Intent, now exceeds 6,500 offices and this figure continues to grow as we work towards our next big milestone of 7,500 offices.”

Quirk, of eMoov, is banned from listing his properties on OTM or being a shareholder of the business because he runs an online agency.

Quirk said that OTM’s revenues are £20m per year, all funded by its member agents.

Of that, £12m goes into marketing. He estimates that most of the rest of the balance goes into salaries.

Quirk said: “OTM’s (or more accurately its member agents’) cost to attract visitors to its website is shockingly expensive.

“We know from OTM’s own statements that they spend around £1m per month on marketing and we also know from their statements that they attract around 5m visits per month, so its members are spending 20p for every visit to a site that is not even their own but shows their competitors.

“Compare that 20p per visit figure to Rightmove’s and Zoopla’s 1p or 2p per visitor.

“Or even compare it to what an agent could spend with Google to get visitors to their own website which would be far more valuable.”

Quirk went on: “One year in and it is time for a serious reality check and for agents to recognise that there is no rational argument for throwing money away and that it is simply an emotional decision.

“And whilst £300 per month may not mean much to many OTM members, the shame is the collective wastage of the industry spending £20m per year on marketing and salaries for nothing.”