Clean air transport is set to be a pivotal issue in tomorrow's London mayoral election, following an announcement from current Mayor Ken Livingstone that he planned to upgrade thousands of taxis in the capital.

Mr Livingstone confirmed that he would retrofit London's entire fleet of taxis to Euro 3 standards, under a proposed three year scheme which would begin next year if he is elected.

The scheme would involve upgrades to 17,000 of the capital's 22,000 registered taxis.

The incumbent mayor told ITV that an extra 20 pence would be levied on each journey to meet the cost of the systems which will be applied to the vehicles in order to reduce pollution.

The increasing severity of emissions legislation and the focus on automotive pollution implies a rise in demand for platinum group metal autocatalysts to control harmful emissions.