ENERGY watchdog Ofgem has asked an independent auditor to investigate the power cut in July which left nearly 100,000 people without electricity.

The investigation, which Ofgem says is normal procedure, will look at the cause of the power failure, and whether it qualifies as an exceptional incident.

It will also look at whether EDF Energy’s actions , or lack of them, were a contributory factor in what happened and whether EDF took appropriate steps to limit the number of customers affected and restored the electricity supply quickly and efficiently.

The power failure lasted for more than three days and was caused when intruders broke into the site in Dartford where the four main electricity cables feeding large parts of Bexley, Dartford and some of Orpington, are carried on a bridge across Dartford Creek.

A subsequent fire severely damaged the cables at a point where no immediate back-up power supply was available.

At the time, EDF Energy declared it had reached agreement with Ofgem that the incident was “exceptional”.

This released the energy company from the obligation to pay £50 to any customer who had been without electricity for 18 hours.

Instead, EDF said it would offer a £50 “goodwill payment” to anyone continuously without power for 24 hours.

A number of people have already criticised the lack of security at the site and others, including Bexley Council, are pressing EDF to offer some financial compensation to those hardest hit by the power failure.

London Assembly member for Bexley, James Cleverly says he wants clarification on whether the incident was “exceptional”.

He said: “I am not holding my breath for people to get more than £50, but it might go some way towards EDF saying sorry.”

He also wants reassurance from the investigation there will be no repetition, especially with the London Olympics looming.

Ofgem says the audit should be ready for consideration by its networks team next month.

If EDF is is judged to have failed in any way, it could suffer financial penalities under the industry’s Interruptions Incentives Scheme.

An Ofgem spokesman explained: "If the audit finds EDF did not perform well during the incident, the minutes of supply lost to customers will go into its overall performance.

"If that results in EDF going below its targets under the scheme, it could lose up to three per cent of its revenue, which could run into millions of pounds."

The company could also come under scrutiny from the Department of Energy and Climate Change, if it is found to have breached the Electricity Safety, Quality and Continuity Regulations.

EDF says it discussed the situation with Ofgem and is not aware of any outstanding issues.

A spokeswoman said: “In our view, under the legislation, this incident was clearly exempt from the Guaranteed Standards of Service.”

Meanwhile there has been no update from Kent police on its investigation.