Two local authorities in Hertfordshire have been revealed among the top five “worst offenders” for approving housing developments on flood plains even when alternatives appear to be available.

Environmental consultant Groundsure looked new build properties across England, specifically the proportion built on previously undeveloped land at high risk of flooding, analysing data from the Environment Agency, Land Registry, and the Department for Communities and Local Government.

Groundsure found two local authorities in Hertfordshire were in the top five allowing building on this kind of land - Dacorum and East Herts.

Dacorum Borough Council topped the list of councils building “unnecessarily” in areas at high risk of flooding.

41 per cent of Dacorum’s new developments, built between 2015 and 2016, were in high flood risk areas, even though this land covers just 2.3 per cent of the borough.

East Hertfordshire was not far behind in fourth place, with 30 per cent of new developments built on high risk flood plains within the same period.

Local authorities in Dartford, Worthing and North Somerset completed the top five.

Dan Montagnani, managing director at Groundsure, said: “Regardless of any flood mitigation measures required by planning and put in place, homebuyers need to consider additional risks and implications that come with buying a home built on a flood plain. 

“While all development in flood plains is subject to stringent flood risk assessment in both design and construction, this data shows that variation in the proportion of development occurring on the flood plain differs hugely from one local authority to the next.”

Dacorum Borough Council said it was not in a position to respond without seeing the report, adding: "Our initial thoughts are that the conclusions about Dacorum are incorrect but without the opportunity to review the report it is not possible to give a considered or evidenced response."