Mitch Ward quit Oakwell in a row over a proposed new deal.
Ward says the club is 'going backwards' despite the arrival of new owner Sean Lewis and thinks other out-of-contract players may leave because of Barnsley's failure to resolve their futures.
"I have just got sick and tired of waiting for everything to be sorted out," said Ward.
"I would have loved to stay but I needed to think about my family's security. I am not the only one, there are four or five others who are out of contract and are being kept waiting.
"Things have got worse," he added. "We were supposed to be going forwards but it has gone backwards since the new consortium came in and took over. I just hope it improves for the sake of the supporters, because they deserve that, but why is everything taking so long?"
Ward says he was offered a new contract by the club but when it came to signing on Monday, the deal was scrapped.
"I asked for a decision at the start of the week because another club had become involved.
"The club is now saying that I have never been offered a new deal but that is simply not true. I have been training and getting on fine with the new manager. He said he wanted to keep me."
Ward claims he is owed 25 per cent of one month's wages, which he agreed to defer until the end of the season, along with three months' pension contributions.
Manager Gudjon Thordarson insisted that Ward had not been offered a new deal and when asked about his departure, said:
"That's a naive question. If he has left, he is clearly not part of our plans."