A survey of 14 "eco" laundry tablets, toilet cleaners and nappies found almost half made claims the firms did not support with convincing evidence.
Scientists commissioned by the magazine Which? said toilet cleaners all made at least one green claim that was not proven by the manufacturers.
Tesco Naturally says it contains no phosphates and leaves no hazardous chemical residues. But neither do regular cleaners.
Sainsbury's Cleanhome is said to be "kinder to the environment and biodegradable" but there was no convincing evidence to show it had a different impact on aquatic life from the market leader, despite the independently assured EU Ecolabel.
The scientists also had reservations about Green Force's claim "formulated to limit the impact on the environment" and were unconvinced by Ecover's ecological qualities.
Ariel and Persil have logos on their laundry tablets suggesting they encourage greener behaviour, but the experts said these benefits were not clear.
Ecover's tablets do not contain chemicals such as optical brighteners, which it says are not easily biodegradable, although there was no convincing evidence to show chemicals found in rival brands would have any worse impact on aquatic life.
And although environmental claims on six nappy and eco-wipe products stood up, some were vague and made it harder for shoppers to differentiate between products.
John Twitchen, of green communications agency Sauce Consultancy, said: "Products targeting green consumers have a responsibility to be clear and unambiguous. While claims may be scientifically proven, the evidence has to be accessible to the average consumer."
Which? editor Martyn Hocking added: "When companies make clear green claims, it helps consumers make eco-choices with confidence. But our experts concluded many companies did not provide enough evidence to back up their claims."
Tesco said it had now removed the phosphate claim from its toilet cleaner but added that in the case of accidental contact, citric acid and naturally derived detergents were "much kinder to the skin".
Sainsbury's said: "The Ecolabel scheme is an independent initiative endorsed by Defra and the EU. This gives our customers credible independent assurance of environmental credentials."