The most definitive research to date has been done for the first time on the overall size of the agency market.

A joint exercise by Rightmove and The Property Ombudsman indicates that there are 20,000 individual sales and lettings offices in the UK.

The figure is at the top end of most estimates, which have had to be worked out from a variety of sources, including TPO, Rightmove, estate agents’ registrations for anti-money laundering, and business registrations under data protection laws.

The new figure has been worked out by using TPO’s membership of almost 25,000 sales and lettings members – although some operate as dual agents, sharing the same premises.

Rightmove data reveals an estimated 9,000 dual agents. Taking this figure away from the 25,000 and adding the estimated 4,000-plus offices that are not currently members of TPO, leads to the estimated 20,000 total.

In addition, figures from Rightmove shows that there are 2,500 new homes developments currently being marketed by larger house builders.

Ombudsman Christopher Hamer said: “Whilst it is a legal requirement for sales agents to register with an ombudsman scheme and we have more than 95% of sales agents in membership with TPO, new legislation is expected to come into force later this year which will make it mandatory for letting agents to register with an approved scheme.

“As the only scheme operating its own unique Code of Practice to raise standards in the industry, 11,500 lettings offices have voluntarily registered with TPO and this figure has steadily increased over the past year.

“We estimate there could be as many as 4,000 additional lettings operations on top of this, although this figure will only be confirmed after the new legislation comes into force.”

Miles Shipside, Rightmove director and housing market analyst, said: “We noted a pick-up in new office openings last year and especially sales offices so far in 2014 as the recovery started to spread beyond London.

“Sales transactions, which include new-build, are running at over 20% higher year-on-year.

“While new-build is about 10% of overall sales activity, it is a very integrated market sector, as buyers’ behaviour is to mix resale and new-build properties together when they search on the internet.

“Home hunters in the UK therefore have to search the property stock from at least 22,500 separate offices and large developments to get a full property picture.”