Ian Paisley Jr has claimed the Protocol is bumping up prices by 27% in Northern Ireland due to "transport and energy" costs.
DUP MP Mr Paisley made the claims speaking on the BBC's Nolan Show but did not share the source of the statistic.
The DUP did not respond to a query from the Belfast Telegraph asking for further information.
On the radio programme on Monday morning, Mr Paisley said the cost of living is a "crucial issue" and said the Northern Ireland Protocol, which his party have railed against, is driving up prices.
He said; "The protocol is adding 27% additional costs to everything in Northern Ireland, because of the additional costs associated with the protocol. That's the cost of transporting things over and the added costs the protocol adds to those transport costs. If you think costs of living are high in GB mainland, people in Northern Ireland add another 27% because of higher energy costs, because of the protocol. if we don't get this fixed, we're going to have a continuing downward spiral of even worse costs," he said.
In the lead up to last week's election, the DUP said that the UK government must act over concerns about post-Brexit trading arrangements before it will nominate ministers to sit at Stormont. Additionally, the DUP has not said whether it will nominate a deputy first minister if Michelle O'Neill, of Stormont's largest party Sinn Fein, becomes first minister.
Mr Paisley said: "One of our five points in our manifesto was that we need to fix the protocol. The weeks before the election was called, one of the reasons why the Assembly was in such crisis was because we had already indicated that our first minister would be pulled out of government, which we did and is not going back into government until we get the protocol fixed."
The North Antrim MP's comments come less than a week after party leader Sir Jeffrey Donaldson claimed in a BBC NI leaders' debate the average cost of groceries is higher in Northern Ireland than in Great Britain.
He quoted Kantar grocery research data commissioned by a DUP-led Stormont department and which was not initially available to the public .
The statistics were quoted by Sir Jeffrey during the television debate, in which he said the price for dairy products has risen by 8% and by 19% for chilled convenience goods, something he said was a direct result of the Protocol.
But was later unveiled by the Department of Economy and showed that the consumer typically pays more on average for groceries in Great Britain than in Northern Ireland.
A spokesperson said: "The figures indicate that in December 2021 the average total grocery price in GB was 8% higher than in NI."
When asked earlier this week if Kantar states the price rises are directly linked to the Protocol, Mr Donaldson further told the BBC: “Yes, it demonstrates that the additional costs are linked to the increase in extra customs checks, delays in transporting goods, additional paperwork and additional staff that have to be employed [as a result of the Protocol].”