An "urgent investigation" has been launched after dozens of confidential social services files, including notes on the Victoria Climbie case, were found at an old town hall being used as a set for a TV drama.
The documents were left on public view on shelves and tables at the former civic centre in Southgate, the set for the police station in the new Inspector Morse drama series.
Tory MP David Burrowes, who discovered the files while campaigning, said he was shocked at Enfield council's negligence.
"It is an abuse of information and negligence and it's completely unacceptable," he said.
The investigation, by Enfield council, must look at "why this has happened and why there has been such negligence to the most sensitive of files", he added.
Any number of people could have looked at the documents, which were left lying next to props marked "Holby City NHS" from a previous filming, the MP for Enfield, Southgate, said.
The documents included memos on the case of eight-year-old Victoria Climbie, who died in 2000 after months of abuse, which were marked "strictly private and confidential".
The files also contained details of parents turned down for adoption, the phone numbers and addresses of vulnerable people on the service's register, and financial information, Burrowes said.
The town hall was mothballed two years ago and is now being used as Cowley Police Station, the set for the Endeavour drama series, the prequel to Morse, starring Shaun Evans as the young detective.
Burrowes said he was holding a surgery for constituents and campaigning for the town hall to be used as a school instead of a television set when he saw some files marked "foster panel minutes" and "adoption files".
He checked to make sure there was nothing sensitive, but "lying around on the table were these files and, almost on the top, was an original file with a big sticker marked Victoria Climbie," he said.
"The files were in a room near the old debating chamber, next to the one that will be used as the chief inspector's office in Endeavour."
A council spokeswoman said: "Enfield Council takes its responsibility to keep confidential information safe and secure very seriously.
"Now that this matter has been brought to our attention we are conducting an urgent investigation to establish the facts."
A spokesman for the Information Commissioner's Office, to whom Burrowes complained, said: "We are aware of this incident and are making inquiries."