The keeper was critical of the Dens Park boss and his coaching staff in a recent interview and Brown today has hit back and alleged that the player recorded an argument the pair had.
The former Celtic keeper says he was only informed that the club had signed a replacement, Stoke keeper Steve Simonsen, just before the announcement was made.
Douglas also says he was told by Brown to “pack his bags and f*** off”.
Brown told the Daily Record: “He’s told a pack of lies and had a dig at people in the backroom staff and myself over the treatment he was given.
“He was injured going into the derby game against Dundee United and couldn’t kick a ball. I had a decision to make and we did well to get a quality goalkeeper, Steve Simonson, in at short notice.
“When it happened, I gave Rab his place by phoning him to tell him that Steve was coming in. I asked him to come into the office for a chat about the situation.
“When he got into the office, the player was raging. He called me a ‘sh*****’ and a ‘c***’.
“I’ve been in the game a long time but I’ve never heard a player talk to a manager in that manner.
“I did the only thing I could do after being spoken to in that manner - I told him the collect his gear and f*** off out the building.
“He then went out into the corridor and kept shouting abuse at me in front of the youth players and some members of the first team squad. It was an attempt to undermine my position there but it didn’t work.
“I could have sacked him there and then for the way he spoke to me but I took into account the years of service he had given the club and placed him on gardening leave.
“I didn’t want him about the place but by not sacking him I gave him the chance to keep picking up his wages until the end of his contract on May.”
Brown said he was willing to five Douglas another chance but was informed by Douglas in a second meeting that the earlier conversation between the pair had been taped.
He said: “Despite all that had been said, I was ready to give him another chance a week later and asked him to come in for another meeting.
“That’s when he told me he’d taped the first meeting.
“He’s now saying he’s the fittest he’s ever been. I don’t know if that’s true or not but if any manager comes to me for advice about signing him, I would tell them to be wary of employing him.
“Here’s why - he didn’t have the decency to tell me he was recording everything that went on in that room and for me that is a betrayal of trust that is unforgivable.
“I wouldn’t have had a problem with him taping what was said if he’d told me in advance.”