More agents, including Strutt & Parker and Winkworth, and now Humberts,  have announced that they will no longer be using Zoopla when OnTheMarket launches.

Humberts yesterday (December 29) became the latest agent to say it will stick with Rightmove.

Ian Westerling, managing director of Humbert, said: “We’re delighted with the proposals and truly believe in its future success. The January launch will be an exciting time for buyers, vendors and agents alike and we’re much looking forward to being a part of it. For us, Rightmove was the obvious portal of choice – Rightmove generates the most leads for us across our branch network and they are committed to providing Humberts with excellent support.”

The Winkworth decision will not apply across the entire network, as not all Winkworth franchisees are members of Agents’ Mutual.

Michael Fiddes, head of agency at Strutt & Parker, said: “We look forward to supporting the launch of the new property portal in January which will offer prospective home buyers a greater level of choice.

“We will also continue to market all of our properties on Rightmove, which remains the UK’s largest property portal.

“Our clients will always be our number one priority, and after much deliberation and careful analysis of web traffic and number of leads generated to our clients, we have decided that this is the best possible combination of portals for our clients.

“Our properties will continue to be marketed on our own website, with over 270,000 visits per month, as well as through the Christie’s International Real Estate website which receives over 212,000 visits per month.”

Fiona Stewart, head of marketing at Strutt & Parker, said: “We have spent time reviewing all of our portal and online marketing plans to ensure that we have the best overall digital strategy in place for 2015.

“We believe the combined digital exposure generated from our own website, and Rightmove, in addition to all of our other marketing activity, will ensure that our properties reach the best potential buyers, both in the UK and internationally.”

Winkworth CEO Dominic Agace said that he believed that OnTheMarket “will quickly become the go-to portal for customers searching for their next property”.

He added: “Those of our offices which are members of Agents’ Mutual will, in addition be marketing properties on Rightmove.

“We believe that these two portals, together with the traffic and leads generated by our own website will ensure that our clients receive the best possible online exposure for their properties.”

Jackson-Stops & Staff, with 44 offices operated by licensees, and London agent Douglas & Gordon, have also announced they are coming off Zoopla.

In a statement on its website, Jackson-Stops & Staff said: “ is expecting many more to join in the coming weeks as momentum continues to grow. Its member agents will be moving hundreds of thousands of properties to from other websites to create a unique set which cannot be found elsewhere.

“When launches, neither Rightmove nor Zoopla will be able to claim their property listings cover the entire market because many estate and letting agents will be leaving them to join as the best platform to showcase their properties in the clearest and simplest way.”

* Despite the recent announced departures of several agents, including Knight Frank and Spicerhaart, Zoopla shares have risen on the stock market.