Both sides of the Old Firm have criticised the SPL over their plans to resolve the end-of-season fixture crisis.
The SPL have produced two sets of fixtures dependant on whether Rangers reach the UEFA Cup Final. The season will be extended to Thursday 22 May if Rangers defeat Fiorentina in the semi-final. Should Fiorentina progress to the final at Rangers' expense however the league will be completed as scheduled on Sunday 18 May. In either scenario, the Ibrox team will face four games in the final eight days.
When Celtic reached the UEFA Cup Final in 2003, the SPL re-arranged the calendar to ensure the club had a full week to prepare for the final and Rangers chief executive Martin Bain could not hide his disappointment that a similar compromise could not be reached.
"Yet Rangers are the only club being asked to play four games in eight days, so there is no sporting integrity.
"It is hardly the best preparation in the lead-up to the Uefa Cup final - if we get there - to play Sunday, Wednesday, Saturday in advance of that. So I don't see what the SPL have done for Rangers in terms of aiding them in European competition."
Celtic chief executive Peter Lawwell also vented his frustration at the SPL.
"We do not want to disadvantage Rangers should they reach the Uefa Cup final, but we are extremely disappointed and concerned at the manner of the decision-making process - which was done without consultation with the clubs or the SPL board - and the effects on the integrity of the competition," said Lawwell.
"In addition, this decision, which will cause a great deal of inconvenience to our supporters and to five other clubs, will also mean that Celtic would have a gap of 11 days before playing our final league fixture.
However, SPL secretary Iain Blair said there was no alternative to extending the season.
"It is well documented that this has been an exceptionally challenging season in terms of fixturing," he said.
"It is a modest extension to the season to enable Rangers FC to represent the SPL and all of Scottish football in the Uefa Cup final.
"It reflects the fact that the outstanding fixtures cannot reasonably be played in the available time and will involve some disruption for a number of our clubs."