'Full-frontal attack on democracy' as London overrules Scottish parliament for the first time

The UK government decided to block a Scottish law on changing gender on Monday, risking a standoff between London and the devolved government in Edinburgh. 

The law -- passed by a wide margin in December with support from all five political parties in the Holyrood parliament -- makes it easier for people to legally change their gender, but is now opposed by London over concerns about its possible impact on UK-wide equality laws. 

This is the first time London has used its legal powers to block a law in Scotland. 

Under the Scotland Act of 1998, a devolved government was created in Scotland, which gave the country a greater say over how it is run. But many areas of law and policy remain under London's control, which is the supreme authority. 

Monday's move risks sparking another political and legal battle between London and Edinburgh, just two months after the Scottish parliament was prevented by the UK Supreme Court from holding a second independence referendum. 

Secretary of State Alister Jack, the UK government's representative in Scotland, said on Monday evening that the gender bill would "impact" how equality legislation functioned across Britain. 

"My ruling today is about the impact of the legislation on the operation of equality protections," he said. "I did not make this decision lightly."

Writing on Twitter, the Scottish First Minister Nicola Sturgeon denounced a "frontal attack on our democratically elected Scottish Parliament and its ability to make its own decisions".

She said the Scottish government would "defend" the law, slamming the "Westminster veto".

The law, proposed by the Scottish parliament in December, aimed to simplify the legal process for changing gender.

It removed the need for transgender people to