BBC News' Jonty Bloom on the NAO report

According to figures compiled by the National Audit Office (NAO), competition has driven down prices sharply, given consumers greater choice and provided them with better service.

Consumers who stayed with their old gas provider have seen prices fall too, but not by as much as those who checked out the market for competitive offers.

OFGAS DG Callum McCarthy: Denies that customers find it difficult to switch suppliers

There is just one group of consumers that is being left from the price cuts - and they are those who would need it most.

Some 1.4 million people, the majority of them the less well-off, use pre-payment gas meters to settle their bill. Gas companies are not fighting to attract this market and price competition is weak.

Loyal to British Gas

There are 20 million gas customers in the UK, spending about £6bn a year.

The majority of them are still loyal to former monopolist British Gas, but four million have switched to one of the 25 new suppliers.

Switching should involve no hassle for consumers. The gas pipe, the meter and the company maintaining the network remain the same. Only the name of the company supplying the gas does change - and the amount charged on the gas bill.

Price confusion

Many customers, though, are wary to switch. Most gas tariff schemes are confusing and difficult to compare with that of rivals.

Ofgas, together with consumer group Which, are producing a fact sheet that attempts to tell consumers which companies are cheapest.

According to their calculations, British Gas's standard credit tariff is "currently one of the highest on the market".

But the Gas Consumers Council says that consumers will find it difficult to compare prices as each company has a different way of charging for gas.

Some demand standing charges, but have lower rates for gas. Others have no basic charge, but have a higher price per cubic metre of gas.

Then there are numerous discount schemes, e.g. for paying by direct debit or buying both gas and electricity from the same supplier.

A survey commissioned by the NAO and Ofgas, the gas industry regulator, showed that 27% of those polled found it difficult to compare prices, while 30% found it easy.

Another problem are dubious sales tactics, where doorstep sellers try to pressurise or mislead consumers into signing a contract.

However, a large majority of the 2,500 people questioned in the poll found it easy to switch to a new supplier - even if they had not done so themselves.

Transfer complaints

Most customers are satisfied with the quality of service they receive from their gas providers.

However, Ofgas and the Gas Consumers' Council received more than 45,000 complaints about transfers during 1998 alone.

Some suppliers appear to be dragging their feet when letting customers go.