A few weeks ago I appeared before the National Energy Regulator of South Africa (Nersa) and made an impassioned plea on behalf of the residents of Johannesburg, urging it to reject Eskom's obscene request for a 15% tariff increase for each of the next three years.

My argument was simple. The residents of the city, and indeed all South Africans, cannot be expected to shoulder the burden of Eskom's inefficiencies and the impact of years of looting and corruption.

In the same week that we saw the return of daily load-shedding, we were informed that Eskom is technically insolvent.

Despite their inability to provide the country with a stable supply of electricity, Eskom's tariffs have risen by a compounded 368% over the past decade. Were Nersa to grant their last request for a 15% increase over the next three years, the compounded increase since 2008 would amount to 608%.

Eskom is now approaching Nersa with the argument that the only way to save the entity from collapse is to increase the cost of energy to consumers. Eskom is now holding the proverbial gun to Nersa's head in an attempt to have consumers subsidise a decade of corruption and mismanagement.

As the mayor of the City of Johannesburg, my perspective is that Eskom has become the greatest threat to Johannesburg.