Almost $5 million is being spent on advertising to encourage NSW motorists to use the E10 ethanol blend, despite warnings that a state government scheme that forces petrol stations to sell the biofuel increases prices.

Documents tabled in the NSW Parliament also reveal that even though the campaign was launched in May, not one retailer has met a requirement under laws introduced this year that E10 must account for at least 60 per cent of all petrol sold.

Even though the campaign was launched in May, not one retailer has met a requirement that E10 must account for at least 60 per cent of all petrol sold.

On January 1, the NSW government introduced new rules that force a wider range of petrol stations to sell E10.

The government said the move was designed to "put downward pressure" on the price of E10 to provide a cheaper alternative for motorists.