Boris Johnson has told a virtual meeting of Conservative MPs that devolution had been a “disaster” in Scotland.
Mr Johnson also reportedly described it as predecessor Tony Blair’s “biggest mistake”.
The SNP and Labour have both criticised the prime minister.
But Communities Secretary Robert Jenrick said Mr Johnson has “always supported devolution”.
“What he does feel strongly, and I would agree, is that devolution in Scotland has facilitated the rise of separatism and nationalism in the form of the SNP, and that that’s trying to break apart the United Kingdom. Anybody, like the prime minister, who loves the UK wants to keep it together thinks that that’s a very, very dangerous and disappointing outcome that we need to battle against.”
Mr Johnson was in a Zoom meeting with Tory MPs representing dozens of seats in northern England on Monday when he is said to have made the remarks.
The Sun newspaper reported the PM had told the MPs “devolution has been a disaster north of the border”.
Many on the pro-UK side have agreed with Mr Johnson’s assessment highlighting the failures of the SNP Government in education, health and many other areas.