Michael Gove has dismissed criticism of the UK government's controversial internal market bill as "myth-making" and "lurid fantasy".
The Scottish government is refusing to put the legislation forward for a formal consent vote at Holyrood.
Scottish ministers say the bill would "undermine" the devolution settlement and over-ride decisions made by MSPs.
Mr Gove told a Holyrood committee that criticisms were "stories to scare children at bedtime", not real policy.
And the Cabinet Office minister said the bill would result in a "net accretion of powers to the Scottish Parliament", leaving Holyrood "stronger within the framework of the UK".
The UK government has clashed with the EU over provisions in the Internal Market Bill which ministers admit would "break international law" by overriding parts of the Brexit withdrawal agreement.
They are also locked in a dispute with the devolved administrations in Scotland, Wales and Northern Ireland about what the legislation could mean for trade and regulations across the UK from January 2021.
The plans as drawn up would allow each administration to set standards and regulations locally, but they would have to accept goods from all other parts of the UK as part of a system of "mutual recognition".
Mr Gove said this was important to ensure that "high quality Scottish produce has unfettered access to the rest of the UK".
But the devolved administrations say it could spark a "race to the bottom".
The bill is expected to complete its passage through the House of Commons on Tuesday evening, despite being opposed by Labour, the SNP, Liberal Democrats, and some senior Conservatives - including former Prime Minister Theresa May.
The Scottish government has put forward a legislative consent memorandum at Holyrood decrying the bill, saying it "risks more uncertainty and confusion for businesses and consumers" and "encouraging harmful deregulation".
It says "a wide range of concerns" have been raised "across a range of sectors, including farming, business, the environment and public health".
This means the Scottish government will not bring forward a formal vote of MSPs on whether to give devolved consent to the bill, although ministers say they will table a debate so members can make their feelings clear.
Mr Gove told MSPs on the Scottish Parliament's constitution committee that there would be no "race to the bottom" in regulations, saying the UK government had been a "world leader" in environmental and animal standards.
He said: "The idea the UK government would compromise our high animal welfare standards is for the birds.
"It may be a lurid fantasy for some that it's the secret agenda of the UK government to use this as a Trojan horse to privatise the NHS, but that's one of the most absurd, ludicrous and irrational fantasies I've heard in my political lifetime. The NHS is not for sale under any circumstances.
"There are some people who are anxious to spread myths about the UK government, but if you look at the evidence you will see the way we have supported the NHS and invested in the NHS in an unprecedented way. The whole thing is ludicrous."
Mr Gove was also pressed on whether or not the UK government would go ahead with the bill even if MSPs do not give their backing to it.
The Sewel Convention states that the UK government would "not normally" legislate across devolved areas without the express consent of devolved administrations.
Mr Gove said "nothing would give me greater pleasure" than winning consent for the bill from MSPs, but said "leaving the EU is not a normal occurrence, it is an exceptional one".
While he said the UK government would not halt the progress of the legislation, he said "we will seek to properly and better understand any concerns" and make amendments in the Lords if needed.
Scottish Constitution Secretary Mike Russell said the bill would undermine "virtually all" of Holyrood's responsibilities, adding that the claim of new powers coming back from the EU was "simply not true".
Mr Russell told the BBC's Good Morning Scotland programme: "The reality of the situation is that they're pointing to things that the Scottish Parliament already does - for example agriculture subsidy and food standards.
"What we're being told is that any framework that exists will not be set by the EU and negotiated, it will be imposed by the UK without consultation.
"This is actually substantially worse than the situation under the EU, even for a Brexiteer, which I'm not.
"I think the work we were able to do as part of the EU raised standards significantly - what the UK is trying to do is lower standards, and say we can't do anything unless they say so."
Other parties also hit out at the bill, with Labour's Alex Rowley telling Mr Gove that "you will pave the way to independence, not the SNP".
Scottish Green co-leader Patrick Harvie said the evidence against the bill was "damning", saying it would "undermine the Scottish parliament's very purpose by enabling Tory governments to veto any decision that threatens their right-wing deregulation agenda".