Okay, there are several hypotheticals in this post, but they are not too far-fetched, I hope.
I expect that there is quite a lot of information out there that could hurt Trump. Whether it is the Steele Dossier or financial data, I would expect Intelligence agencies around the world to have access to them.
Trump’s policies are hurtful to many countries’ interests.
So, when do you think those countries might have enough and have those anti-Trump tidbits published?
Or might the fact that this has not yet happened (as far as I know) mean that there is no dirt on him or that there is a certain honour among thieves (or a gentlemen’s agreement) about not hurting other Governments’ leaders?
Our allies probably won’t because it might hurt trust once someone rational returns to the White House.
Our enemies won’t because when your opponent is screwing up, you don’t want him out.
Now if Trump started standing up to the Russians, like implementing the sanctions, we might see something. A leak, as it were.
Intelligence agencies and associated individuals who have info on Trump wrongdoing are doing the sensible thing and giving this information to theFBI
Come out in public with it? No, not really, because that undercuts all the American institutions that are supposed to be dealing with the Orange Horror.
There’s only two types of information that a foreign intelligence agency could have - information about Trump’s lawbreaking, or information about his being a massive shit. Publicising the second sort is clearly useless, since America is divided into those who already know he’s a massive shit and those who will never know it. Publicising the first sort could screw up actual ongoing criminal investigations. Why would anyone who cares about justice do that? (People who don’t care about justice would, of course, be heading off to the whitehouse for their blackmail money instead)
If a foreign government had damaging information about Trump, they wouldn’t immediately publish it. They’d approach Trump first and threaten to publish it if he didn’t do what the foreign government wanted. So let’s add a third alternative to the ones you mentioned; the dirt exists and Trump agreed to their demands.
I think that “allies” and “unfriendly” are words undergoing something of a fuzzy redefinition at the moment.
I don’t doubt that the UK, having a major intelligence service, will either have or be attempting to acquire compromising material on Trump. They’d be idiots not to seeing as he is a loose cannon and some form of restraint may be needed in the future.
As to how that is used? well, unlikely to be a direct UK leak, probably through a third party but as always when considering where it came from just consider “cui bono” (who stands to gain?)