Another analyst, Credit Suisse, was also busy yesterday on the subject of the UK portals.

It said that it sees limited threat from Agents’ Mutual to Rightmove and Zoopla – although it warned that the threat is “real”.

It also expects Agents’ Mutual to reach its recruitment target of 5,000 agents by launch.

Yesterday, the bank slashed its target price for Rightmove from 3,100p to 2,655p, and for Zoopla from 290p to 270p – while reiterating its ‘outperform’ rating for both.

Credit Suisse said: “We conclude that Agents’ Mutual membership is growing, the risks are real and will impact Rightmove and Zoopla 2015 numbers, but that with the stocks down 13% and 17% respectively over the last month, the risks are priced in.”

It went on: “However, funding for Agents’ Mutual may be insufficient.”

Credit Suisse compared Agents’ Mutual pot of £9.4m in 2014, and £22m next year, with Rightmove’s and Zoopla’s annual spend of between £42m and £46m.

Credit Suisse also said that newsflow would be “negative” in the short term for both Rightmove and Zoopla as Agents’ Mutual membership continues to grow, but that the latter’s medium-term impact would have only a limited impact on its two competitors.

The bank said: “Around launch, newsflow will likely shift as the venture actually has to deliver on the promises made to agents.

“We flag launch delays, poor site usage, weak early traffic and a lack of leads as potential issues.”

Rightmove shares ended yesterday at 2,063.50, up 43p (2.12%) as the company continued its share buy-back policy.

Zoopla shares were 201p, down 1.20p on the day.