The body in charge of Britain's electricity network has given assurances that the lights will stay on this winter after concerns were raised by some of its engineers.

The National Energy System Operator (NESO) said the country's electricity system was prepared and "resilient to the challenges it may face" during the colder months.

However, its winter outlook report comes after an independent investigation found engineers had "high levels of stress and concern" about their ability to ensure adequate supply due to differences between renewable and gas-fired power generation.

NESO said supplies were expected to remain secure throughout the winter, though warned there could be "tight days".

It added that such days would result in it deploying notices to power producers that additional electricity generation may be needed. It said such an announcement was not a warning of power cuts and was routine.

"While we never take resilience for granted, households and businesses can be confident that Great Britain's electricity system remains secure, reliable and among the most resilient in the world," said Deborah Petterson, director of whole energy system resilience at NESO.

In a separate report, National Gas, a private company that owns and runs the country's gas network, and is separate from NESO, said it expected to have sufficient supply to meet demand this winter, but forecast gas for power generation to increase at peak demand due to the "intermittent" nature of renewables.

The release of the two reports comes as Britain's energy generation and security falls under increasing scrutiny, given the wars in the Middle East and eastern Europe have pushed prices up and sparked supply fears.

The country's electricity is generated from a wide range of sources, including renewables such as solar and wind, as well as more traditional gas-fired and nuclear power stations.

Wind power was the largest generator of electricity in Britain last year, accounting for almost 30% of all power, marginally above gas.

However, there appear to be challenges in the transition to renewables in ensuring supply keeps up with demand, according to findings from an investigation into practices at NESO, which was commissioned following allegations over operational decision making and record keeping at the grid operator.

Law firm Eversheds Sutherland, which carried out the independent investigation, said there were "high levels of stress and concern" within NESO's Electricity National Control Centre over the "current state of the energy industry generally" and the longer-term ability to keep it balanced.

It said this was, according to evidence gathered from staff, due to the fact that traditional methods of electricity generation such as gas were "easier to manage", compared to renewables, which were "less flexible", and were making the job of ensuring supply meets demand "more difficult".

The probe also found there to be a "significant disconnect" between those working in the control room and NESO's leadership.

Multiple witnesses expressed the view that those in senior leadership and executive positions "do not fully appreciate or understand either the way in which the control room works, or the reality of the pressures faced by those on the frontline who are responsible for 'keeping the lights on'", Eversheds' report said.

The investigation was prompted after Conservative shadow energy secretary Clare Coutinho said in July she had been contacted by a whistle-blower alleging that NESO had been "hiding information about how securely our grid is being run".

One of the claims was that control room staff were encouraged to conceal or alter records to avoid leaving a paper trail linked to efforts to stabilise the grid during a period of extreme heat in June.

This was done in order for NESO, which is owned by the government, to avoid public scrutiny or reputational damage, according to the allegation.

Eversheds said its investigation did not substantiate any of the allegations from whistle-blowers but did identify "cultural, governance and control issues" that it said were "significant findings in their own right".

Fintan Slye, chief executive of NESO, said the investigation identified "areas where we could improve how colleagues can raise concerns and how we respond to them".

"I want all colleagues at NESO to feel heard. We will act on the recommendations, working closely with our trade unions, and be open with colleagues about the progress we make," he added.