It's not new information really.
https://dorseteye.com/the-labour-party-must-now-suspend-peter-mandelson/
Mandleson continued to be in touch with Epstein AFTER his first conviction. That's more damning in some ways, you could sort of if you squint make an argument that Mandleson had no idea Epstein was a bad guy when he wrote in the birthday book. But by 2009 everyone knew what he was and Mandleson was still in contact with him.
This has been known about for ages and it hasn't affected him negatively. Mandleson himself when challenged a while back basically said he was only friends with Epstein for the money and connections. Which...
I can only assume that other political parties haven't drawn much attention to this because they are waiting till close to the next GE. It's what I would do if I was Reform/a right wing paper because it is pretty damning. God knows what Labour are thinking. I can understand the need to have someone in America who can ooze up to Trump in a real politic sense but there has to be someone else.