The government package is aimed at reducing bills over the coming years
Gordon Brown has come under fire for saying all pensioners will get free home insulation - when it will go only to over 70s or those on benefits.
The PM made his promise on Thursday when he unveiled a £910m energy saving plan agreed with the power giants.
But when Heather Tarn, 60, from Beaconsfield in Buckinghamshire, called the government's helpline she was told Mr Brown had made a mistake.
The Tories said Mr Brown's much-touted energy package was "unravelling".
But the government said the deal was clear.
Unveiling the package of help for energy consumers on Thursday, Mr Brown said: "All lower income and all pensioner households will be eligible for free loft and cavity wall insulation and other energy saving measures that could save them up to £300 a year in their energy bills."
But a Department for Environment, Food and Rural Affairs (Defra) spokesman confirmed only pensioners over 70 and some pensioners on benefits were eligible for free cavity wall or loft insulation. Discounts are available for others.
Mrs Tarn said: "Of course I was disappointed but I feel worse for all the other pensioners who can ill afford it. He's made a mistake and he shouldn't be running the country."
At Thursday's press conference, Environment Secretary Hilary Benn said the offer "was very, very clear".
He went on to explain: "For pensioners, for people on low incomes and other benefits, the loft and cavity wall insulation is available free, for others at 50% of the cost that you would otherwise pay, and we are working with the energy companies to build capacity."
Mrs Tarn, a constituent of a Conservative MP, was told by the government helpline that she was not eligible for cavity wall insulation.
The helpline adviser told her: "Gordon Brown made a mistake."
A Downing Street spokesman said: "The purpose of the PM's presentation was to announce a package of assistance of help that is available to all households, and the enhanced assistance available to those households that are eligible including pensioners and those that are on lower incomes.
"Consumers should speak to the helpline or check the details on the website what help is available to them."
The BBC understands the helpline has received a number of calls from younger pensioners disappointed that they were not entitled to as much help as they thought.
Shadow business secretary Alan Duncan, for the Conservatives, said: "Gordon Brown's long-awaited energy announcement is unravelling further by the day.
"This is yet more evidence that despite having months in which to prepare, the government still rushed out a scrambled package that lacks clarity on even the most basic points.
"People might wonder whether the prime minister made a big mistake or whether he was deliberately trying to mislead people.
"It's now even clearer that Gordon Brown's long-term economic recovery plan was more to do with his own short-term political survival."