Update: As most were predicting, London Mayor Ken Livingstone has given the green light to the £25 ($50) daily charge on high emissions sports cars and SUVs that drive though central parts of the UK capital. The new scheme will come into effect on October 27, forcing vehicles with the highest greenhouse gas emissions to pay the fee every time they enter London’s Congestion Zone.

Original: It's almost too much to believe, but London is contemplating a £25 daily tax on 'gas-guzzling' cars. We've covered the tax before, but Londoners could be feeling the pressure of the bill in the very near future - the tax bill will be decided this week. The goal is not to inflate city coffers to the bursting point - although that's likely to be the short-term result - but rather to help London cut its carbon emissions by 60 percent by 2025. Whatever the justification, those entering London in SUVs, older cars, or other somewhat less than efficient vehicles will be faced with a dilemma.

What makes a gas-guzzler in London? Emitting more than 225g CO2 per 100km - which works out to vehicles with a fuel efficiency of less than 24 mpg US or 9.78L/100km. That's sure to be a fair portion of the traffic that currently enters the city each day. The plan had originally included an exemption for London residents within the taxed zone, but that exemption has been removed for drivers of four-wheel drive and luxury cars, reports Reuters UK. While that certainly shows an increased attention to the green goals of the project, one has to wonder why the exemption isn't removed for all vehicles - are highly polluting cheap cars desirable, while luxury cars are to be despised? Or should highly polluting two-wheel drives be treated any differently from their more off-road capable brethren?

Owners of such non-exempt cars who continue to drive in London each day will be forced to pay £6,500 (roughly US$13,000) annually. That's just a bit short of the price of some small hatchbacks - new - in the UK, and would buy any number of petrol-sipping econo-cars used.

The tax - if passed - will become part of the city's larger green initiative, which includes promoting the use of bicycles in the city, fitting new filters to city equipment and buildings and the low-emission zone targeting heavy trucks, which went into effect on Monday in the zone encircled by the M25.