A revision of the moratorium on oil and gas exploration through hydraulic fracturing introduced Thursday infuriated Bulgarian environmentalists.

The modification introduced Thursday by the ad-hoc parliamentary committee on shale gas removed a provision specifying that the pressure used in oil and gas drilling cannot exceed 20 atmospheres.

The change was requested by oil and gas companies who said that the ban was blocking exploration and production activities of conventional gas.

Mariana Hristova and her colleagues from "Civil Initiative for a Ban on Shale Gas Exploration and Production through Hydraulic Fracturing" threatened renewed protests and civil unrest.

The environmental activists argued that the change technically lifted the ban on the unconventional gas development through hydraulic fracturing.

Hristova noted that the environmentalists' proposal to include definitions of conventional and unconventional sources of oil and natural gas into the moratorium had been ignored by MPs.

She explained that the inclusion of the definitions would delineate cases in which the deployment of hydraulic fracturing is forbidden, thereby preventing obstructions to conventional drilling.

Hristova said that the change introduced on Thursday practically "opened the doors" to the activities of Park Place, which is drilling in the village of Vranino near Kavarna, Direct Petroleum, which is drilling near the village of Deventsi and Rusgekom, which is drilling near the village of Rogozina in Dobrudzha.

The modified text of the ban is yet to be voted in Parliament.