MPs are calling for the government to split up the company that runs Britain's electricity system and create an American-style network with an independent system operator (ISO).
National Grid's share price dropped by 1.27 per cent in morning trading.
17 June 2016 @ 11:30amNational Grid (NG.)
The report, from the cross-party Energy and Climate Change Committee, said: "The government should set out its intentions regarding an ISO as soon as possible, and consult on a detailed, staged plan for their implementation, so as to avoid injecting uncertainty into the energy sector."
The National Grid - a privately owned company listed on the FTSE 100 - owns the main electricity infrastructure in England and Wales, such as national pipes and pylons. However, the firm also has stakes in two interconnector power links with the continent and plans to build more, raising concerns it is conflicted.
The report said: "National Grid continues to dominate this market. We would like to see greater competition for new interconnector developments in the future, particularly given potential conflicts of interest relating to National Grid's interconnector holdings."
Angus MacNiel, the committee chair, said: "National Grid's technical expertise in operating the national energy system must be weighed against its potential conflicts of interest. The independent system operator model has worked in the USA. It is time for it to be brought to these shores."
National Grid said: "We take very seriously the need to provide confidence that any potential conflicts of interest are handled correctly and have a lot of experience operating in an environment where this is a key part of what we do.
"We are currently working with the government and with regulators to ensure we continue to manage potential conflicts as our role develops."