“It will not be appropriate for ministers individually to advocate for specific options or opine on the likely outcome of the process.”
However, there is precedent for Prime Ministers to temporarily suspend collective responsibility during debates about Europe.
Harold Wilson allowed Cabinet ministers Michael Foot, Tony Benn, Peter Shore, Barbara Castle, Eric Varley, William Ross and John Silkin to vote to leave the European Economic Community in 1975.
David Cameron also suspended collective responsibility when Michael Gove, Chris Grayling, Iain Duncan Smith, John Whittingdale, Theresa Villiers and Priti Patel backed Brexit in 2016.
Tory leader Kemi Badenoch accused the Prime Minister of having “opened his mouth without engaging his brain” after sparking a row about freedom of movement.
In a fiery row at Prime Minister’s Questions, Mr Burnham replied: “There is no confusion at all.