The city of Groningen has seriously underestimated the potential risk of earthquakes from its sustainable energy plan, a government watchdog has warned.

The Staatstoezicht op de Mijnen (SodM), which regulates mining and underground activities, also said the WarmteStad project, a joint initiative of the city council and water supplier Waterbedrijf Groningen, lacked sufficient expertise.

The province has become more susceptible to earthquakes in recent decades as a result of gas production destabilising the ground. Three years ago Groningen launched a plan to supply heat from ground source pumps, which aims to make the city carbon neutral by 2035.

SodM is carrying out a risk assessment on behalf of the ministry of infrastructure to determine whether it is safe to proceed with the project. It said a seismic risk assessment was needed because the drilling is taking place close to the gas field.