Dog walkers Paul and Simon Cook were left outraged after finding a semi-naked woman posing for explicit pictures with an amateur photographer at Sandall Beat Wood in broad daylight on Sunday afternoon.
Said Paul: "It is not just the kind of thing that should be taking place somewhere where there are children near by.
"The woods are very popular with families and there were quite a lot of people around at the time. It's wrong."
Mr Cook, a children's football coach, and his brother, were walking their dogs near a disused water pumping station in the wood at the bottom of the Straight Mile at Doncaster Racecourse when they spotted a young woman in a state of undress.
"At first we thought it was a young girl - we were about 30 metres away," he said.
"She walked across the doorway wearing just a jumper with her bottom half totally uncovered. Then she spotted us and tried to pull the jumper down to cover herself.
"Then the photographer appeared and tried to block the doorway and that's when we confronted him and asked him what was going on."
The pair filmed the exchange with the photographer, a grey-haired man in his 60s, wearing a blue top, while the woman, who Mr Cook believes is in her 30s, can be seen using her mobile phone in the background.
Clearly flustered at being caught and filmed, the snapper says: "We're not doing any harm, come on lads, she's a professional model. I'm not trying to cause any trouble."
The man filming replies: "It's not appropriate to be doing this in Sandall Beat. We've walked past and seen her semi-naked."
The photographer responds: "I take your point. We're all grown ups. We're not trying to cause any trouble. We'll wander back to the car and b*gger off."
Mr Cook said: "They pretty much 'fessed up that they were in the wrong. The woman was saying we were perverts and had been watching.
"I told her that if we we were, we wouldn't have confronted them and told them to stop and shift."
Mr Cook said the route where the man and woman were spotted is a popular path used by children for pony trekking as well as walkers and cyclists en route to a large outdoor play area.
He said he has now passed the video to police who are investigating and added: "From what I have heard since, it is not the first time this photographer and woman have been seen in the woods taking explicit photos."
The wood, at the end of the Straight Mile at Doncaster Racecourse, has always been a popular spot for walkers and cyclists.
But it has also got a long unwanted tag as a spot for outdoor sex and 'dogging' activties, especially after dark with many couples using the secluded car park at the entrance to the woods for sex.
We have contacted South Yorkshire Police for comment.