Salt company Frisia Zout has been given the green light to mine salt from under the Wadden Sea, saying there is no evidence there will be a significant effect on the sea bed.

Junior economic affairs minister Sharon Dijksma has enraged environmental groups by her decision, which they say will have a serious impact on marine life, the NRC reports.

The Dutch sea research institute NIOZ had also warned about the consequences of allowing drilling, saying the sea bed is likely to drop and sandbanks will shrink, which will threaten the habitat of tens of thousands of migrating birds.

Appeal

Other reports, including those carried out on behalf of Frisia, said the only effect is likely to be that sandbanks grow less quickly.

MPs had earlier called on the minister not to approve the permit if there is any doubt about the likely effects on the Wadden Sea, which is a Unesco heritage site. The environmental groups say they will appeal.

There has been considerable concern in Friesland itself about the plan. In 2007, Frisia agreed to pay compensation after a combination of salt and gas extraction led to a 33 cm drop in the ground level in the north west of the province.

The minister says the permit has been granted on condition there is continual monitoring and that salt extraction will be reduced or even stopped altogether if the monitoring reveals problems.