A gas-powered tourist bus is now making its first journeys across Oxford.

Guide Friday, which runs The Oxford Tour, is converting its fleet of double-decker tour buses from diesel to liquefied petroleum gas in the next 18 months, and the first service was launched yesterday.

LPG fuel is more refined than normal petrol and produces fewer dangerous emissions.

City councillors hope the switch will mean less long-term damage to Oxford's historic buildings.

Liberal Democrat city councillor Tony Brett said: "The tour company has had the idea that by making the switch they will be helping to preserve Oxford's famous historic buildings.

"They know that they need to protect the very buildings tourists pay them to see in Oxford.

"I am sure that the city centre is going to benefit greatly from this environmental initiative. I hope that it is the first of many."

Twenty city council vehicles out of a total of 200 run by the City Works division are also run on LPG fuel. A further 17 are electric.

Building firm Knowles & Son, which is based near to the tour company's depot in Osney Mead, has offered Guide Friday a base for refuelling.

Eight buses in the Oxford fleet will eventually run on liquefied petroleum gas provided by Calor.