He said: "I would like to say sorry to all Port Vale supporters for the humiliating defeat.
"It was the lowest point of Vale's proud FA Cup history which has seen so many great achievements over the decades.
"Like all Vale fans I am absolutely gutted."
Chasetown who are four divisions below the football league, couldn't believe their luck as Vale captain Luke Rodgers missed two penalties in the second half.
The fairy tale was completed when 19-year-old schools football coach Danny Smith headed in an 89th minute winner to send his team into a third round clash with Championship side Cardiff.
The 500 travelling Vale fans responded to the defeat by chanting 'You're not fit to wear the shirt' just as they had done after the initial 1-1 draw at Vale Park.
Bratt added: "It will not do any good castigating the players.
"We need to get behind the team and return to winning ways in the league campaign."
The Vale chairman showed his support for manager Lee Sinnott who he believes is the right man to take the club forward.
"I would urge supporters to rally round and back our manager, who I am convinced, given time and support, will bring back the good times to Vale Park.
"Vale fans have known plenty of low points over the years but, through thick and thin, they support the club they love with tremendous spirit.
"We need this spirit and support now, more than ever."
After the 1-1 draw at Vale Park manager Sinnott made his players stay out on the pitch so they could witness the celebrations from the travelling Chasetown support.
He wanted to get a reaction from them to ensure that a result of this nature would not happen again.
It seemed to work as Vale created the better chances throughout the contest but they could not convert against their part time counterparts who defended for their lives.
Sinnott refused to put any blame on his players after the match and said: "No one could have scripted it any better for Chasetown, but it wasn't for our lack of trying.
"No one can level anything at our players today - they have done everything except win.
"We didn't deserve this result but that is the way it has gone but I cannot fault the players for their commitment and I would like to stress that.
"You have to ride storms and we're not going to sulk about it or go into our shell. We will come out kicking and screaming and fighting about it."
Vale will look to put their manager's positive words into practice as they host tenth place Tranmere on Saturday.
An encouraging away win at Gillingham lifted them off the bottom of the table last week and a second win in a row would surely vanish any sour memories of the FA Cup second round match.
Sinnott will be hoping the fans have already put the defeat behind them as he hopes for no negative support.
" The players certainly don't deserve a backlash from this game. If the fans want to react like that then in my view, that is playing into the hands of Tranmere."
It has been a rocky start for Sinnott who has guided his team to just a solitary league win since his appointment on November 5th.
The loss of star strikers Leon Constantine and Akpo Sodje in the summer who scored a combined forty two goals between them last season has restricted his options up front.
Previously Sinnott managed non league outfit Farsley Celtic guiding them to three promotions in four seasons.