The Government has lost an opposition vote calling on it to publish impact assessments of Brexit on over 50 key industries.
There was no official division – as only Labour MPs backed it and no Tory MPs objected.
Speaker John Bercow said he "expects" the Government to respect the decision – despite confusion over whether the result is binding.
Opposition day debate motions are traditionally non-binding, but Labour had tabled a special 'Humble Address' motion.
It is a centuries-old and infrequently used procedure that asks The Queen directly to request documents from the Government.
Mr Bercow had advised earlier: "Motions of this kind have in the past been seen as effective or binding."