The Energy Retail Association says the big six utility firms it represents will resist Government demands to pass on falling prices in the wholesale markets until early in the new year.

The Chancellor is equally likely to defy pressure from some lobby groups and MPs to introduce a windfall tax, but he is expected to force the energy companies to plough more funds into tackling fuel poverty.

The chief executives of the companies were last week summoned to Whitehall by Energy Minister Ed Miliband to explain why domestic fuel bills have not been reduced, even though wholesale gas and electricity prices have plummeted.

The meeting was the second this month as political pressure mounts on the Government to curb the soaring profits of energy companies such as Scottish Gas owner Centrica.

During a visit to Scotland last week, Dr Garry Felgate, chief executive of the association, said: "I would be surprised if you saw any price reductions this side of Christmas. The price we are all paying over the next months is already paid for. What the energy companies have done wisely is pre-buy for winter. We live in a very, very competitive market. There are six energy retailers and they compete on service and price. As and when they can (pass on cuts in the wholesale markets], they will do so."

Energy analysts estimate the industry could afford to reduce domestic bills by as much as £150 per household per year after wholesale prices for gas and electricity tumbled by more than 40% in the past couple of months.

The energy companies' refusal so far to pass the savings on to consumers has led to mounting pressure on the Government to legislate.

CBI Scotland director Iain McMillan warns against the introduction of energy-related taxes. "It is crucial that the PBR does not contain any nasty surprises that could put at risk much needed development of our indigenous North Sea oil and gas reserves. At a time of growing concern about security of energy supplies, Britain ought to be trying to get as much as possible out of the North Sea with a stable and supportive tax regime."

Options for the Chancellor include requiring energy firms to introduce a "social tariff" for the 5.5 million British households which consumer watchdog Consumer Focus estimates are living in fuel poverty. He is also thought to be looking at a programme to make poorer households more energy efficient.

But the Energy Retail Association says further taxation on the industry will prevent utility firms from investing in new power stations and updating infrastructure. Felgate said the Government was relying on the private sector to make much-needed investments in the National Grid, for example, but energy companies would not stump up the money if they feared more prohibitive taxes.

In the worst case scenario, he warned, a failure on the part of Government to encourage energy companies to invest in infrastructure now could result in energy shortages in the future. "Government is not going to pay for it," he said.

"It's incredibly important the energy companies know what the playing field is.

"Windfall taxes are very damaging for that."