Boris Johnson has vowed to bring forward measures to “compensate for the grave inadequacies” of the Scottish government.
In an interview with BBC Scotland ahead of the Conservative party conference, the prime minister attacked the SNP for their record on health and education.
He ruled out allowing a second referendum on Scottish independence.
And after a furious debate in the Commons on Wednesday, he defended his use of strong language.
Mr Johnson said that, following either a deal or a no-deal Brexit, he would bring forward measures to produce “a much stronger Scottish economy”.
He said: “They (the SNP) have the highest taxes anywhere in the UK. They are not doing a good job on health, they are not doing a good job on education.
“I hope the money that we are now investing is properly spent on those services.
“And I hope that Scottish Conservatives get the credit they deserve for the hundreds of millions of extra funding that we’re putting into Scottish agriculture which was secured, not by Nicola Sturgeon, but by Scottish Conservatives.”
Chancellor Sajid Javid announced an extra £1.2bn for Scotland earlier this month – including £160m for farmers to settle a long-running row over the redistribution of Common Agricultural Policy payments.
Mr Johnson, who has called for opposition parties to immediately back a general election, also refuted SNP claims that they have a mandate to call a second Scottish independence referendum.
Nicola Sturgeon has said she wants to hold a poll on the issue in the second half of 2020 – but the UK government would need to transfer power through a Section 30 order to allow another referendum to take place.
She has previously said it would be “unthinkable” for Mr Johnson to remain as prime minister after the Supreme Court ruled he acted unlawfully in suspending Parliament, and has urged other opposition leaders to back a vote of no confidence that would remove him from office and trigger a general election.
Mr Johnson said: “We had an independence referendum in 2014 and we made an explicit promise to the people of Scotland that this was going to be a once-in-a-generation event.
“The people of Scotland voted very, very substantially to stay part of the UK, which was the right decision as this is the most successful union anywhere in the world.
“They were promised this was a once-in-a-generation thing and I think we should stick with that.”
Mr Johnson also responded to criticism over his use of strong language in Parliament and defended his description of a law seeking to block a no-deal Brexit as “the surrender bill”.
The law, known as the Benn bill, forces the government to ask for an extension to the Brexit deadline.
The prime minister insisted he “deplores any threats to anybody, particularly female MPs”, after he described one MP’s safety concerns as “humbug”.
But he again refused to apologise for the words he used.
Mr Johnson said: “No. I have to stand my ground there because if you can’t say or use a word that is very common in political discourse, like surrender, then you’re starting to impoverish the language.
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“The best way to take the heat out of it all is just to get Brexit done, and my experience is both Leavers and Remainers in this country- most people – just want us to get out on October 31.”
He added: “What I said was that the surrender act – the Benn act – is very, very disappointing because what that does is it gives the EU the power to decide in negotiations how long the UK must remain in the EU.”
Responding to Mr Johnson’s remarks, the SNP’s deputy leader, Keith Brown, said: The reality is that the SNP Scottish government is delivering for people and communities, while under the Tories’ zombie administration Westminster has completely stopped governing.
“People across Scotland are looking on in horror at the chaos engulfing Westminster and the Brexit disaster being imposed on Scotland by Boris Johnson and his extremist cabal in Downing Street.
“Support for independence and for an independence referendum is growing, and a win for the SNP in the coming election will demonstrate that.”
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