Economic affairs minister Erik Wiebes has written to 200 of the Netherlands’ biggest companies telling them they should stop using natural gas from the Groningen fields within four years, broadcaster NOS said on Tuesday.

Instead, companies can either switch to sustainable sources or use a different sort of natural gas to that from Groningen, the letter states.

The ‘phasing out’ of Groningen gas is ‘unavoidable’, the minister said in the letter. Companies themselves should decide how best to make the transition to alternative energy sources.

‘My ministry will be in touch with you shortly to talk about the issue and reach a joint decision,’ the letter states.

Groningen gas, is known as ‘low calorific’ gas and is used mainly by private households and a ‘few large industrial companies.’ They will have to adapt their equipment to cope with the higher calorific gas from abroad, which has less nitrogen.

Gas users lobby group VEMW told the Financieele Dagblad that converting to take a different sort of gas is a ‘complex operation’ which cannot be completed by 2020.

During last week’s debate on the earthquakes in Groningen, which are caused by the land settling after gas has been removed from under the province,’ MPs called on Wiebes to take more concrete steps to reduce the problem.

Thousands of houses have been damaged by the quakes.