The Tories have had 14 years to change the laws to better protect single sex spaces.
In truth, they probably are not the easiest laws to successfully change because the European Court of Human Rights have determined that people have the right to be legally recognized as their chosen sex. Laws that impede on that could be subject to legal challenges and, possibly, a declaration by the ECHR that the law is in violation. A successful change is probably going to require a detailed analysis into where single sex spaces are justifiable and proportionate.
The Tories nominally started this process by writing to the Equality and Human Rights Commission for a preliminary analysis on the virtues of introducing the concept of biological sex into the Equalities Act (a move that Starmer professed to support). The Equality and Human Rights Commission did give a response with some guidance but the Tories have sat on their hands ever since. It was widely speculated that they wouldn’t actually move ahead with changing the law, so that they’d be able to campaign on the issue at the next - i.e. this - election instead). It seems that is exactly what has happened - instead of changing the law they have left it unchanged so that they can try and win votes by promising future changes if re-elected.
Frankly, I’m skeptical that the Tories would actually see this process out if re-elected. They’ve had the time and means to make changes but seem to have deliberately avoided doing so and it hasn’t been high on their legislative agenda.
For what it’s worth, Labour have also pledged to clarify the law on single sex spaces, to protect single sex spaces. I have similar doubts as to whether they’d follow through, too.