The association, which represents 90 per cent of the 900 bus operators here, gave the reassurance at a press conference yesterday that it was not fixing prices.

Its chairman, Mr Wong Ann Lin, 60, said the Competition Commission of Singapore had met association officials on Friday to remind them not to violate anti-competitive rules by fixing prices.

School bus operators can still decide how much to charge, said Mr Wong, but if parents find the increase is way above the recommended rate of $5 to $10, they can file a complaint with the association.

One parent had earlier complained to the association - about an operator who wanted to increase his fares by $30 to a new rate of $70 a month.

Mr Wong said: 'I met the bus operator and told him the problem lay with him - why did he charge $40 in the first place? As a parent, if the fares are suddenly increased by so much, of course I won't be happy.'

The operator settled on a $10 to $15 increase.

Mr Wong also explained the need for the hike next year. 'With diesel prices rising, bus operators were asking us if they could raise fares and by how much, to cover their operating costs.'

For a $5 increase, a one-way trip works out to an increase of 11 cents a trip, said Mr Wong.

Diesel costs, which make up about a third of a bus operator's total expenses, have more than doubled from 73 cents a litre in 2004 to $1.52 this year.

In a report on operating costs and fare-setting strategies published in 2005, fuel costs were found to make up an average of 33 per cent of annual operating costs of a bus operator, or about $10,000.

Mr Wong said most HDB families pay an average of $50 a month for a child's school bus fare although operating costs range from $65 to $170 a child.

The association is putting a copy of this report up on its website and has given copies to school principals so that parents can read it for themselves.

But even increasing fares by $10 a month will not mean more pay for bus operator Foo Nyuk Leong, 55. He said it would help lighten the burden of his operating costs, but not cover them completely.

The father of two children in their 20s, who earns $1,500 to $2,000 a month, said: 'I still have to work at night to ferry restaurant or karaoke staff home, to help cover the costs.

'It's very tiring, having to work early in the morning, and then at night.'

wycin@sph.com.sg