JK Rowling has tweeted a picture of herself in a T-shirt that calls Scotland’s first minister a “destroyer of women’s rights”.
The author also gave her support to people protesting over a new gender recognition law in the country.
She posted: “I stand in solidarity with @ForWomenScot and all women protesting and speaking outside the Scottish Parliament. #NoToSelfID.”
The legislation aims to amend a previous law to make it easier for transgender people to be legally recognised as their chosen gender and get a new birth certificate.
They will no longer need to provide medical reports or evidence, and the minimum age of applicants for a Gender Recognition Certificate (GRC) will be cut from 18 to 16.
A majority of MSPs on a parliamentary committee have recommended that the general principles of the Gender Recognition Reform Bill should be approved.
Scotland’s social justice secretary has said it won’t give trans people new rights but is about “simplifying and improving the process for a trans person to gain legal recognition”.
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In a statement, Shona Robison said: “Our support for trans rights does not conflict with our continued strong commitment to uphold the rights and protections that women and girls currently have under the 2010 Equality Act. This bill makes no changes to that act.”
People protested against the planned law outside the Scottish Parliament in Edinburgh on Thursday.
Some carried signs reading “no one was born in the wrong body”, “humans can’t change sex” and “keep prisons single sex”.
Former Scottish Labour leader Johann Lamont said the committee “should listen, they should challenge, they should argue, they should probe”.
She added: “They should not dismiss, because in that world of dismissal, you shoot the messenger. You ignore the message, you make bad law and other people live with the consequences.”
Rowling has been criticised by some over her views on women’s rights and trans people but strongly denies being transphobic.
In January, police said they wouldn’t charge trans activists who tweeted photos showing her address – so-called “doxing”.