Greens say the ceremonial mace fits easily into the Toyota Prius

Oxford council voted to replace Bryan Keen's ageing car with a �22,000 BMW, because of the company's local plant.

But he will now get a petrol/electric Toyota Prius, which Greens say is cheaper and causes half the pollution.

There was concern Mr Keen's ceremonial mace would not fit in the car, although Greens say they have disproved this.

Some Labour councillors had argued that it was important for the lord mayor to drive a car made by BMW, because of its plant in Cowley.

But Craig Simmons, a Green councillor, used special powers to force executives to look again at the decision to buy Mr Keen a BMW in August.

If the first citizen doesn't do the right thing, how can we convince ordinary people? Craig Simmons, Green

At a second vote on Monday, five Labour members of the executive backed the BMW plan, while three Labour members, a Liberal Democrat and Mr Simmons voted against.

Chairman Alex Hollingsworth, a Labour councillor, had the casting vote against.

Mr Simmons told BBC News Online: "Oxford has an appalling air quality problem. If the first citizen doesn't do the right thing, how can we convince bus and taxi companies and ordinary people to choose low-emission vehicles?

"This is a major achievement. Otherwise it would have been a case of do as I say not as I do."

The lord mayor has rejected a Green Party suggestion to buy a bicycle and a bus pass, although the council says he regularly takes buses.

An Oxford City Council spokeswoman said: "It was suggested a BMW would be good choice because of the plant in Oxford.

"However, it was found that it could not be converted to produce lower emissions, so the Toyota is more environmentally-friendly."