Stuff like this makes me really question how they are trying to 'balance the books' as they say, as if they need to submit some kind of file before a deadline and this ticks that box.
They've literally been told it's a bad idea, but through what I presume is a mix of pressure and optics, as well as some flawed assumptions specifically on CGT as alluded to in the below, you can just bet that they're plugging previous years much larger takes into a spreadsheet that increases top rates by ~20% into the next few years and they'll be happy they've 'fixed it' without any consideration for either the reality of it or what any direct effects or beyond might be!
Hiking capital gains tax to 45% would be possibly the most moronic policy yet adopted by Labour. They seem unable to get it into their thick heads that this would result in a significant reduction in tax revenues.
Capital gains tax is a voluntary tax, only levied when people choose to sell an asset for a gain. If Labour hugely hiked the rate people just wouldn't sell.
HMRC itself has made clear that raising CGT to 45% would result in a reduction in revenue of at least £7 billion.