Celtic announced on Monday that the ban - which had been announced 24 hours earlier in a bid to prevent the use of pyrotechnics - had been shelved following a U-turn by St Johnstone and Police Scotland.
However, police confirmed the ban remained in place and it is understood confusion arose after a Celtic official accidentally called his Inverness counterpart instead of his colleague at St Johnstone to discuss the issue. Celtic face Inverness in the Highlands on Sunday.
Celtic's statement remains on their official website but St Johnstone are expected to clear up the matter later on Tuesday.
St Johnstone's initial statement on Sunday said both the Perth club and Celtic fully supported the police decision, which was taken to stop fans using banners as a shield to allow them to let off smoke bombs and flares.
But Celtic then said: "Following discussions today between Celtic, the local police and St Johnstone FC, it has been decided that flags and banners will now be permitted at the match on Boxing Day.
"We have an excellent relationship with everyone at St Johnstone FC and we thank them and the police for reviewing their initial decision.
"Football is about colour and atmosphere and creating a positive occasion for all and everything should be done to ensure that such an event can take place."
That was later contradicted by police who stressed there had been no change in policy, which had been agreed following talks between both clubs, and that Celtic had signed up to the first statement.
The confusion came as Motherwell began work to replace more than 250 seats which were broken by Celtic fans during their Fir Park meeting on December 6.
Police said that 18 smoke bombs, three fireworks, and one flare had been set off inside the ground. A number of arrests have been made as police probe the vandalism inside the ground and several disturbances outside.