Some files of Facebook documents have been seized by MPs investigating the Cambridge Analytica data scandal.
Parliamentary powers that are rarely used were used to demand that the boss of a US software firm hand over the details.
The Observer, which first reported the story, said the documents included data about Facebook’s privacy controls.
MP Damian Collins later said he believed the documents were “highly relevant” to his inquiry. Facebook has demanded their return.
The documents were intercepted when an executive of US tech firm Six4Three was on a trip to London.
In a highly strange move the House of Commons serjeant-at-arms was sent to the businessman’s hotel and he was given a final warning and a two-hour deadline to comply with the order.
When the executive failed to do so he was escorted to Parliament and warned he risked fines and imprisonment if the documents were not surrendered, the paper said.
The firm is involved in court action against Facebook in the US, where the documents were obtained through legal procedures.
Facebook told the Observer: “The materials obtained by the DCMS committee are subject to a protective order of the San Mateo Superior Court restricting their disclosure.
“We have asked the DCMS committee to refrain from reviewing them and to return them to counsel or to Facebook.”
But Damian Collins, chairman of the Commons Digital, Culture, Media and Sport (DCMS) Committee, said he believes the documents – which include emails – contain important information about how Facebook and other parties handle user data.
He said he had written to Facebook stressing the House of Commons had powers to seize documents within UK jurisdiction.
In his email to Facebook public policy vice president Richard Allen, which he posted on Twitter on Sunday evening, Mr Collins said a committee of the House can publish these documents under parliamentary privilege.