Bulgarian Minister of Environment and Water Neno Dimov was charged with the deliberate mismanagement of water supplies for the western city of Pernik, prosecutors said on Friday.

Dimov faces up to eight years in jail for allowing water supplies to industrial users even when he had been informed that the water in a dam - the only source of drinking water to the city of 70,000 - has seriously decreased, prosecutors said.

Dimov resigned earlier on Friday.

Pernik, a town with a population of more than 70,000, has been subject to severe and continuing water restrictions for about two months, a matter that has been under investigation by several institutions.

Earlier, Prime Minister Boyko Borissov said Dimov's job was a matter for discussion with the ruling coalition partners.

In the third Borissov government, formed in May 2017, Dimov was nominated to the post by the minority partner in the coalition, the nationalist United Patriots.

The Prosecutor's Office said in a statement that Chief Prosecutor Ivan Geshev visited Pernik on Thursday to coordinate actions in the investigation connected to pre-trial proceedings regarding the water crisis in the town, which lies about 25 kilometres (16 miles) west of the capital Sofia.

"Evidence is being collected of crimes committed by officials that led to water supply problems in Pernik," the office said in a statement.

The Socialist Party - the largest opposition party - said it would file a no-confidence motion against Borissov's government, accusing it of failing to ensure proper water and clean air policies, resulting in the water restrictions in Pernik, and serious air pollution in many Bulgarian cities.

The motion is unlikely to pass, as the government enjoys the support of a small populist party and can secure a parliamentary majority.

Prosecutors have focused their investigation on possible mismanagement - whether local officials from the supply company and the municipal administration have taken appropriate steps to ensure the water supply to Pernik and several nearby towns.