THE State Government will double its liquefied petroleum gas subsidy for motorists converting family cars to gas in the wake of crippling fuel prices.

Premier Alan Carpenter said the Government would provide $1000 towards each LPG conversion for at least the next four years, following a review of the six-year-old scheme that until now has provided a $500 subsidy.

Mr Carpenter said many WA motorists were paying more than $100 a week for petrol.

``This subsidy will allow motorists to at least consider (converting their cars to gas) because there are no signs the price for petrol will come tumbling down,'' he said.

``The potential savings of using LPG are becoming bigger and bigger.

``A major issue in our economy is the price of petrol.

``We have an alternative (fuel) in LPG from our own gas reserves.

``We have abundant volumes of gas here in WA and we'd be crazy not to use it.''''

LPG is substantially cheaper than petrol and produces 20 per cent less greenhouse gases.

Under the subsidy scheme owners of family vehicles are eligible to receive the $1000 subsidy for either the conversion of an existing vehicle or the purchase of a new vehicle fitted with an LPG system.

Most taxis in WA run on LPG.

Mr Carpenter said the benefits of LPG to WA highlighted the need to put aside some of the state's offshore gas reserves for domestic use.

Mr Carpenter said countries like Japan, Korea, China, the US and India were lining up to buy WA gas.A lack of competition between coal and gas could see the price of electricity become two or three times dearer.

`` We have to make sure we have secure gas supplies,'' Mr Carpenter said.

``What is happening is that overseas buyers are looking at the way the gas price is going and the growth and demand of their own economies and are signing up gas volumes in long-term contracts when they become available.

``There is the prospect for WA that there will be no gas available for the domestic market because all of it is contracted for sale in the international market.

``We can't allow that scenario to happen.''

He said WA gas producers owed it to WA to look after the domestic market.

``The whole industry in WA was based on the people of this state guaranteeing to buy the gas in the first place,'' he said.