Households in fuel poverty are usually defined as those which spend more than 10% of their income on keeping warm.
But the Environmental Audit Committee said the government was redefining the amount of people counted as 'fuel-poor' – reducing the number of households from 3.2m to 2.4m overnight.
Committee chair Joan Walley said: "The government is shifting the goal-posts on fuel poverty so that official statistics record far fewer households as fuel-poor."
Changes to the fuel poverty definition and target should be stopped unless the government was prepared to make a public commitment to end fuel poverty altogether.
The government should not weaken its commitment to 'eliminate' fuel poverty as it made changes to 'green levies' that funded energy efficiency improvements for the poorest bill payers.
"A short-term bid to cut bills must not throw energy and climate change policy off-course."
In the longer term green levies, could actually keep bills down if they drive energy efficiency improvements that cut the cost of heating our homes.
"Insulating homes and supporting green technologies is vital to help the fuel poor and cut the emissions causing climate change."
Energy subsidies played an important and justified role in alleviating fuel poverty, according to a new report from the committee.
The committee also argues that the government should use the forthcoming Autumn Statement as an opportunity to provide a clear and comprehensive analysis of energy subsidies in the UK.
This would bring much needed transparency and provide a basis for an overdue debate on the rationale for energy subsidies in the UK, it says.
To reinforce the need to cut the emissions causing climate change, the MPs also call on the government to reduce the proportion of overall energy subsidies that support fossil fuels.
The government is expected to respond to the findings in due course. The full report can be downloaded here.