European Commission-funded research found up to 20% of products - including ovens, fridges, washing machines and dishwashers - did not comply with energy-efficiency standards.
As a result, 10% of potential energy savings promised are missed by millions of products across Europe, the trust said.
The research analysed the efficiency of domestic fridges, testing the energy label declarations over a two-year period between 2009 and 2011.
Philip Sellwood, chief executive at the Energy Saving Trust, a social enterprise group with a charitable foundation, called for more to be done to address the findings of the project.
He said: "We need to address the fact that consumers across Europe are not maximising the energy saving benefits stated by millions of products.
"There is an obvious need to recoup any potential savings through establishing more rigorous market surveillance and standards across energy efficient products and labelling. The European Commission has recognised that this energy wastage is a problem, and is keen to ensure a compelling climate of compliance across all aspects of energy efficiency."
Mr Sellwood added: "From our perspective, it's clear that any labelling needs to be accurate, easy for the consumer to understand and displayed clearly in retailers across Europe."
The Energy Savings Trust will tackle the problem with mystery shoppers, who will test products in an attempt to prevent misleading energy claims.
MarketWatch, as the scheme will be known, will be a three-year programme with more than 300 inspections in shops and 300 in online stores. The trust hopes to check a total of 25,000 products to find out whether they are correctly labelled across Europe.
Mr Sellwood said the programme also intended to help save customers money.
"What we will be doing through our work is establishing how improved market surveillance, energy efficiency labelling and product standards can have the most impact and ultimately lead to greater savings for the UK consumer," he said.
Despite its concerns, findings by the trust suggest nearly £1.3 billion could be saved a year on electricity bills in the UK by switching to more energy-efficient products.
Douglas Herbison, chief executive at the Association of Manufacturers of Domestic Appliances said: "The market surveillance and enforcement for energy labelling already happening across Europe is vital in ensuring that products' energy efficiency claims conform to these requirements."