Consumer groups today warned of "massive" variations in gas bills across the UK if suppliers follow a utility firm's new regional pricing policy.

Scotland's 90,000 npower customers will see gas bills rise by up to 10%.

However, some areas will take much lower hits. In the Highlands, those with meters will face a rise of just 0.3% under the new plan.

And people with pre- payment card meters living in Central Scotland will get a 5.3% cut in bills.

Experts today said they expected other suppliers to follow the lead of npower, which claimed the move was to offset costs, including gas transportation costs.

The change will mean gas price rises of up to 24% for some npower customers in the UK with London and the East Midlands faring worst.

British Gas also said it was considering a regional pricing structure.

But a spokesman said: "We have not implemented anything at this stage."

Campaigners believe the new structure will effectively penalise customers who live far away from coastal gas terminals.

Tim Wolfenden, of the uSwitch price comparison website, said other suppliers would adopt the policy, possibly within a fortnight.

He said this could cause "a huge geographical discrepancy in what customers pay. The losers will feel hard done by".

He said: "If all suppliers go the same way as npower, it will hurt a lot of customers. There will be massive increases in some areas."

A spokesman for consumer body energywatch said: "There is a little variation in gas distribution costs, but there is no way firms can explain differences that see some areas pay more than double the bills of other parts of the country."