Ofgem imposed a £500,000 penalty on Scottish Hydro Electric Power Distribution, £400,000 on Central Networks and £100,000 on Electricity North West Limited for failing to meet deadlines to connect homes and businesses to the electricity system.

Given the need to invest £200bn in UK’s energy industry in the next 10 years, it is vital that customers get prompt connections, especially given the need to expand local renewable generation schemes to deliver secure and sustainable energy supplies for consumers, the regulator said.

Ofgem senior partner for smarter grids and governance Stuart Cook said that customers such as developers of housing estates or wind farms are reliant on local power network companies to provide a good service on connections.

"The penalty sends a clear message that the companies must meet the standards set by Ofgem for connection services," Cook said.