The chances of “price aggression” from Zoopla are set to increase, a City analyst has said, as more agents opt to quit the portal and stick with Rightmove.

Barclays says that shares in Rightmove look “broadly fairly valued and Zoopla extremely inexpensive”. However, it accepts that there is “more short risk associated with Zoopla”.

It goes on to say that OnTheMarket will not be doing anything different from Rightmove and Zoopla.

The report estimates that a total of 4,000 OnTheMarket branches will leave the big two – with 3,000 leaving Zoopla and 1,000 quitting Rightmove.

Glentree Estates – the upmarket agent in Hampstead, London – is however one of those which will stay with Zoopla.

The one-office firm is the last of the Agents’ Mutual founders whose intentions are now clear.

Of the seven original founders, five (Humberts, Knight Frank, Savills, Douglas & Gordon and Strutt & Parker) are opting for Rightmove. Two – Glentree and Chestertons – have chosen Zoopla.

Of the three other agent board members, all have chosen Rightmove. The latest to show their hand is Rook Matthews Sayer in the north-east.

Barclays advise both Rightmove and Zoopla investors to “hang in there”.

The report insists: “We believe that AM won’t get the consumer traction it needs.”

However, it acknowledges that “early Agents’ Mutual trends seem to be in favour of Rightmove” and has lowered Zoopla accordingly.

The report estimates that around 80% of a total of some 770 OnTheMarket branches will stick with Rightmove and drop Zoopla. However, it also acknowledges that the 770 that it knows about remains a small sample.

OnTheMarket boss Ian Springett told Eye this week that over 4,600 offices are now signed up.