I linked the Pilecki report. he was a Polish underground leader who infiltrated the camps and collected info with his fellow patriots for a fair amount of time, and repeatedly smuggled it out to the rest of the underground whom transmitted it to the British, who appear to have kept it pretty quiet.

I presume they did not release or make a big deal about the information to avoid pressure from the public to act on the information for probably two reasons:

• They were a bit overextended already, and detour TO Poland with troops or supplies would be a lot of work
• They didn't want to butt heads with the Soviets, who were clearly looking to grab Poland and Germany (if not more) and who would likely have gone to war with the allies over both, as almost happened with the whole partitioning of Berlin and the airlifts and so on.

Here is one English translation of the report that I have located: https://archive.org/details/WITOLDREPORT/page/n7/mode/2up I don't know Polish so I can't personally verify the accuracy of the translation, however I do have friends that do speak Polish and have verified it.

For what it's worth, the Polish Underground he was a founding member of was one that was in opposition to the other underground organization that was pro-Communist, funded by the Soviets. After the war, he maintained his underground infrastructure and fought the communist regime until they captured him, tried him, and executed him for "fascism". He was certainly NOT a communist.