Martin Lewis has explained why the £2,500 new Energy Price Guarantee won't cap your bills this winter.
It comes after Liz Truss falsely claimed nobody in the UK will pay more than £2,500 on their energy bills.
The Prime Minister took part in a round of local media interviews to defend her budget, which was announced last week.
Talking to BBC Radio Kent, Ms Truss said she was "making sure that nobody is paying fuel bills of more than £2,500".
She also told listeners in Nottingham she was "making sure people across this country are not facing energy bills of more than £2,500".
Mr Lewis has repeatedly warned that there is no cap and the limit is not £2,500.
The money expert clarified that the cap is actually on the standing charges and the unit rates for gas and electricity.
This means if you use more energy, you will also pay more.
He tweeted it to his 1.8 million followers yesterday (Thursday) and tweeted it again this morning after the Prime Minister's comments.
Mr Lewis said communicating that there is a price cap is "risky" because some people, especially if they are vulnerable or elderly, may think they can keep the heating on all the time in winter without being charged more than £2,500.
He tweeted: "The reason it is so important NOT to communicate that there is a £2,500 cap is it risks some people, possibly vulnerable elderly people, thinking they can keep the heat on max all winter, and they won't pay more than a certain amount."
Yesterday, Mr Lewis tweeted: "THERE IS NO £2,500 CAP ON ENERGY BILLS.
"Instead the new 1 Oct guarantee, like the old caps, limits - Daily charge (28p gas, 46p elec) - & Unit rates (10p/kWh gas, 34p/kWh elec).
"So use more, pay more. £2,500 is just what someone with avg use'd pay."
This morning, the PM's comments were criticised by Full Fact, a fact-checking charity, who said she made false claims during her rounds of interviews.
Chief executive Will Moy said: "Liz Truss has repeatedly misled listeners this morning.
"She must now publicly correct her mistake to make sure people are not misled about their energy prices and hit with unexpected and unaffordable energy bills this winter."
The tweet from Mr Lewis came shortly before the article from Full Fact was published, while his tweet did not directly reference the Prime Minister.
In other interviews, Ms Truss correctly referred to a "typical" bill.
However, Uswitch research has found more than a third of households (38%) wrongly believe their bill can't go any higher than £2,500.
It comes as Mr Lewis warned of a mortgage "ticking timebomb" if UK interest rate rises follow market predictions.
Speaking on ITV's Good Morning Britain, the consumer champion suggested those with variable rate mortgages or fixed-rate deals coming to an end should go on a comparison website to see what is currently available.
The MoneySavingExpert.com founder said: "Then check your existing company to see what it will give you and then mortgage brokers are worth their weight in gold right now."
Mr Lewis said that, for some, there may be a logic to breaking their fixed deal, but he added: "It is not right for everyone - you want the mortgage broker to do those numbers."
There have been recent suggestions the Bank of England may need to raise interest rates to as high as 6%.
Mr Lewis said that scenario would be "catastrophic for mortgage holders", highlighting the costs it could add to mortgages.
