Governments in Prague and Bucharest could soon join Sofia in instituting temporary moratoriums on shale gas exploration, reports in the Czech Republic and Romania have claimed.

In Prague, the country's environment ministry said on May 7 that it planned a moratorium of up to two years on granting licenses for shale gas exploration until new mining legislation was passed, Reuters said.

"Existing Czech legislation is not prepared for such technically complicated research like there is in the case of shale gas," the news agency quoted a ministry statement as saying.

The ministry cancelled a provisional shale gas exploration license for Australian-based BasGas in April, claiming that a government commission made legal and procedural errors during the application process, Reuters said.

In Romania, the new cabinet of social-democrat leader Victor Ponta, expected to win parliamentary confirmation on May 7, announced its intention to halt all shale gas exploration until current European studies concerning the impact of hydro-fracturing (fracking) technology on the environment are complete.

If the moratorium passes, US firm Chevron, which was also granted an exploratory license in Bulgaria only to be told later that it cannot use fracking in its exploration, will have to effectively suspend exploration north of the Danube River as well.

Following a strong public reaction against fracking and several protest rallies, Bulgaria's Parliament passed a ban on shale gas exploration in February, but will likely have to amend the wording of the document, since it now bans all drilling for oil and gas at pressures above 20 atmospheres, effectively outlawing any drilling at depths below 200m.

France is another European country to have banned shale gas exploration, but Poland, largely reliant on Russian energy sources and thought to have large reserves of shale gas, has embraced the idea. In the UK, an independent report in April advised the cabinet to allow shale gas extraction.