Striker Jon Parkin grabbed a hat-trick to leave Stanley two points from safety at the foot of the Football League.
Richardson said: "We must take the blame as a group and individuals as it was lacklustre and it wasn't good enough.
"We came into the game buoyant and believing we could win but the first goal killed us.
"But as a club, the fans, the management and the staff - we aren't defeated and, rather than dwell on the negatives, let's be positive.
"There are still a lot of points to play for and I believe we will stay up. I have left the messages in the changing room for the players to think about and it should hurt them.
"We can't mope, we have got to be up for the fight and we can't shirk away or hide. It's a tough job but we have got to still believe and I do."
- Sports & Recreation