Councils are 'routinely ignoring' small plots of brownfield land that could be used to build homes, according to environmental campaigners.
The Campaign to Protect Rural England (CPRE) says a more rigorous approach could unlock land for an extra 188,734 homes.
The warning comes as local authority planning departments are due to publish up-to-date registers of brownfield sites suitable for development by the end of this month.
Proposals for 20% of new homes to be built on brownfield sites were announced in the recent autumn budget.
But CPRE says an initial audit of information submitted so far shows that less than 4% of current registered brownfield land is on small sites.
Its report Unlocking Potential says local authorities 'routinely disregard small brownfield sites', which usually have good rail and road links, access to local amenities and proximity to existing communities.
Rebecca Pullinger, CPRE’s planning campaigner said: 'The current system of collecting this data must be improved if we are to unlock the potential of brownfield, and stop developers finding an excuse to build on greenfield areas.'
A report published yesterday argued brownfield land alone was not enough to meet housing need.