Britain’s decision to leave the European Union could lead to higher energy prices and energy supply shortages if the exit is not managed properly, a report by an upper-house parliamentary committee report said on Monday. Britain imports around 5-6 percent of its electricity via power links with France, Holland and Ireland, while around 40 percent of the country’s gas supply comes via Norwegian and European pipelines.

The report, published by the cross-party House of Lords, said post-Brexit, Britain’s energy trading outside of Europe’s Internal Energy Market will likely be less efficient than the current arrangements.

“This creates the potential for higher energy bills, and leaving the EU could risk supply shortages in the event of extreme weather or unplanned generation outages,” it said, according to Reuters.

The report said the government should carry out a full assessment on the impact of leaving Europe’s energy market and set out plans on how it expects to manage any severe supply shortages.

The EU operates a solidarity principle regarding gas, which means in the event of a serious crisis member states are expected to help each other maintain supplies.

Britain’s role in the arrangement, once it leaves the European Union in March 2019 is unclear.

The report also called on the government to review the possibility of creating a special transition period arrangement for the country’s participation the European Atomic Energy Community (Euratom), separate from the wider Brexit process.