"Consumers face 17 more years of above-inflation increases in energy and water bills as they help pay for the renewal of the UK's infrastructure, Whitehall's spending watchdog has warned.
It expressed particular concern about low-income households.
But the government said it was "committed" to keeping bills down. Fuel costs have become a highly charged political issue in recent months.
Five of the UK's six main energy companies have announced price rises, at an average of 8.1%.
On Tuesday, EDF Energy became the latest provider to increase bills, by an average of 3.9%.
In September, Labour leader Ed Miliband announced plans for a 20-month energy price freeze from May 2015, should his party win the next election.
And the government has launched a competition review and will review green and social charges, responsible for some of the cost of bills.
In an escalation of rhetoric, Liberal Democrat Energy Secretary Ed Davey told an industry conference on Tuesday that firms should not use customers as "cash cows".
In its report, the National Audit Office (NAO) said it was estimated there would be an 18% average real-terms increase in household energy bills between now and 2030. For water, the figure would be 28%....
The NAO expressed particular concern about the plight of the low-income households where energy and water bills accounted for 15% of spending in 2011 - almost double the overall average of 8% -
while their incomes had fallen by 11% in real terms since 2002."...