Goalkeeper Shane Higgs, defender Gavin Caines and midfielder Alex Russell have all been made available for transfer, with Russell tipped to join Port Vale on loan later this week.
Allen said: "I need to improve the starting eleven which costs money. I'd like to keep all my players but I have to work as best I can.
"They're good players but we've got too many players here. If they aren't in the team, they're available. Fact. We haven't been winning games and something's got to change.
"If we were winning, had sell-out crowds every week and were in the top six, then these players would be staying but we've got to do what we've got to do.
"To fill the ground we have to win matches because people will pay to watch a winning team."