Through the float, which OnTheMarket hopes will give it a value of between £200m and £250m, the company aims to raise £50m to fund its growth.
Already the UK's third-largest residential property portal, OnTheMarket wants to launch a "heavyweight" national TV and digital and print media campaign to kick its opponents out of the space.
"For consumers and agents alike, we are committed to creating a genuine agent-controlled alternative challenger business and brand to the two leading incumbent portals," said Ian Springett, chief executive of OnTheMarket's owner Agents’ Mutual.
"We believe that by raising capital from new investors we will substantially strengthen our market position."
A history of rivalry
Agents' Mutual, a company which – as the name might suggest – is owned by a group of estate agents, set up OnTheMarket to wrest control of the housing market back into the hands of agents from tech platforms such as Rightmove.
It became embroiled in a competition-related legal case earlier this year, as it maintained that any properties listed on its site could only make a second listing on either Zoopla or Rightmove – not both.
The case was brought by Cheshire-based estate agent Gascoigne Halman, which joined OnTheMarket but was later sued for breach of contract as its properties appeared on both competitors.
But the Competition Appeal Tribunal was not convinced that there was anything wrong with OnTheMarket's rule, and found that it "did not form part of a wider concerted practice to ‘boycott’" other portals.
Rightmove's shares were trading down 0.94 per cent on the previous close at the time of writing, while Zoopla was up 1.19 per cent.