Peter Kilfoyle, the Public Service Minister, said he was reviewing whether London should be allowed to continue using the prestigious Charter Mark as a matter of urgency in the wake of a dramatic rise in complaints in the past six months.
Offer, the electricity industry watchdog, has compiled a dossier on London disclosing that staff routinely fail to comply with regulations, ignore voluntary codes of conduct and fail to respond properly to customer complaints.
In one instance, Offer had to threaten the company with criminal proceedings to end its practice of changing supply meters, the accuracy of which was in doubt, before they had been checked by an independent meter examiner.
In a letter to the Cabinet Office, Offer's London regional manager said: "The theme running through all this is one of customers being disadvantaged and deprived of their rights."
Last year complaints against London, now owned by the US utility Entergy, rose by 23.5 per cent but specific complaints about quality of supply more than doubled. In its letter, Offer criticises the company over its policy of compulsorily installing pre-payment meters as a means of recovering debt, although metering is only supposed to be installed where it is "safe and practicable".
It also takes London to task for unilaterally changing the terms of direct debit mandates without consultation, describing it as "symptomatic of the high-handed and somewhat arrogant attitude which this company frequently manifests to its customers".
Officials from the Cabinet Office's Charter Unit are meeting the company to decide whether the mark, first awarded in 1995 for excellent service, should be removed.
Under legislation introduced in 1993 electricity customers have an automatic right to compensation where suppliers fail to meet specified standards of service.