Claims that controversial changes to the gender recognition process in Scotland impact on UK-wide equalities legislation are wrong, Nicola Sturgeon has said.

The Scottish First Minister was speaking amid ongoing controversy over the UK Government’s veto of Holyrood legislation.

Former Supreme Court judge Lord Sumption said it is part of a strategy from SNP ministers to “provoke constitutional rows, which they hope will boost support for independence”.

He accused the Scottish Government of “froth and rage” on the issue, as he warned any legal challenge to Westminster’s use of Section 35 powers to block the Gender Recognition Reform (Scotland) Bill would fail unless Scottish ministers address the “serious legal and practical problems” in the legislation.

While accepting legal opinion on the matter is “divided”, Ms Sturgeon nevertheless insisted it is wrong to say the Bill impacts on equalities legislation in the UK.

Speaking on the BBC’s Sunday with Laura Kuenssberg programme, the First Minister said: “I have not heard any argument about the impact on the Equality Act that I find in any way persuasive or compelling, because the Act does not change the legal effect of a gender recognition certificate.”

She defended the Bill lowering the age at which a trans person can obtain a certificate from 18 to 16, saying there would be “greater advice and support available to what would be a tiny number of people of that age group wanting to go through this process”.

She also dismissed the concern of some women’s rights groups who fear the changes could help men gain access to women-only spaces.

Ms Sturgeon said: “You don’t have to show your birth certificate to access women-only spaces. So this Bill does not give a predatory man any more ability to abuse women than that predatory man already has.”

She said differences in policy between Holyrood and Westminster had only arisen because ministers in London ditched their plans to reform gender recognition.

Ms Sturgeon said: “When we first put forward this proposal, the UK Government had exactly the same plans, under Theresa May the UK government was planning to do exactly the same.”

But she said by blocking the Bill – which was passed by Holyrood in December – Scottish Secretary Alister Jack was “exercising some kind of government general-like power to block a democratic decision”.

Hitting out at the UK Government, she added: “They did not raise these concerns with us directly during the process of this Bill, they wait till after the Parliament has passed it and they exercise not something to take it to court but a veto. It is outrageous.”

She claimed the UK Government’s decision had “nothing to do with concerns about the Equality Act”, and accused Conservative politicians of “trying to stoke a culture war” on the issue “because they somehow think that plays well with their base ahead of a general election”.

She also said the move was part of “a pattern of undermining and delegitimising” from the Tory administration in London.

Lord Sumption, however, said “the suggestion that the UK Government’s veto is an attack on Scottish democracy is absurd”.

Writing in Sunday Times, he said: “If the Bill becomes law, some UK citizens will have a different legal gender in different parts of the UK, depending on where they happen to be.

“This poses serious legal and practical problems for employers and public authorities operating on a UK-wide basis.

“They will have to discriminate between trans people in Scotland and the rest of the UK on such matters as equal pay, gender discrimination, tax, benefits and pensions, all of which are subject to UK-wide statutory regimes.”

He insisted “these are powerful points”, which if left unanswered by Scottish ministers could cause any judicial review over the use of Section 35 to fail.

The former barrister added: “For some years Scottish ministers have been promoting Bills in Edinburgh designed to throw grit into the working of the union in the few areas where there is scope for disagreement.

“The strategy is to nibble away at the matters reserved to Westminster in order to provoke constitutional rows, which they hope will boost support for independence.”