Ports manager Pat McGibbon has made the move with the full backing of the Shamrock Park directors but remains reluctant to discuss individual details of any internal club issue.
Two of the most experienced members of the first-team squad will now play competitive games for the reserves’ Premiership Development League squad.
Portadown started the Danske Bank Premiership season with a 12-point deduction imposed by the Irish Football Association and sit with just two wins from seven ahead of Cliftonville’s weekend visit.
But McGibbon considers the move to cut adrift the two established Irish League names his only option at present.
“Both have been told they are no longer in my first-team plans and the club will listen to offers for Mark and Sean ahead of the January window,” said McGibbon. “I do not want to get into specifics but feel a decision had to be made.
“It is not personal but some players are not buying into the philosophy of what we are trying to do.
“I have made the call for what I consider the best interests of the team and club.”
McAllister and Mackle will both become free agents in the summer.
“I have no problem getting dropped relating to form but have felt for some time the manager does not want me at the club,” said McAllister. “I consider it an insult that I’m seen as a bad influence on the squad when anyone who knows me would say the opposite.
“Until my contract runs out I will remain totally professional towards Portadown.
Mackle is one of the longest-serving players on the books at Shamrock Park, having joined the Ports in 2009.
“I do not want to get into details but will just say it is a disappointing way to end my career at Portadown,” said Mackle. “I feel I have been a loyal servant to the club and just want to wish the team all the best for the rest of the season.”