Speculation is mounting that online agent Purplebricks, less than two years old, is to launch on the stock exchange very shortly with a valuation of £230m.

According to reliable sources, however, the firm has placed only 20% of that valuation with investors, for £50m.

It means that shares in just 20% of Purplebricks will be available for trading – with the likelihood that trading may be limited, as new investors may be reluctant to sell.

They will have had what could be described as a Dragons Den moment, where the dragons typically decide to back a relatively small proportion of what is usually a new company with a relatively large investment.

While it is relatively unusual for firms to make a stock market debut offering such a low proportion of its valuation, what it does do is validate that valuation and in doing so, send out messages to the market.

Purplebricks, valued at £230m and launched some 18 months ago, is now worth about one-third of Countrywide.

The valuation of Purplebricks may also prove unsettling for the likes of Countrywide and LSL, who have yet to announce their online strategies.

The launch of Purplebricks is likely to be on AIM according to sources, and will come just days after the Treasury announced that there will be a consultation in the New Year about how to encourage innovation into estate agency, including online-only agents.

Purplebricks does describe itself as having a hybrid model.

A spokesperson for Purplebricks was invited to comment but declined to do so.