Three men dressed as cartoon caveman Fred Flintstone climbed on top of Stonehenge today to protest about Tory leader David Cameron's comments on absent fathers.

The trio, from Fathers 4 Justice, scaled the ancient stones on Salisbury Plain shortly after 9am with supplies to last up to three days.

Matt O'Connor, founder of the group, said the protest was in response to Mr Cameron's "failure to get to grips with the issue of absent fathers in Britain".

Mr Cameron said today that attitudes to gun carrying and absentee fathers had to be altered in the same way attitudes to drink-driving had changed.

"Let's look at what we're going to put in place of gang culture, and the first thing we need to put into place is a family culture and fathers standing by their responsibilities," he said.

Mr O'Connor said: "Mr Cameron says fathers are abandoning their children and this can lead to children getting involved with crime.

"We at Fathers 4 Justice feel very strongly that this is not always the case.

"We ask why is the Government, through the family courts system, preventing dads who want to be good dads from seeing their children?

"Sadly, David Cameron seems to hold the same view on this as the current Labour Government."

Mr O'Connor said the three Fred Flintstones, each wigged and holding caveman clubs, would be on the stones overnight and had supplies for three days.

"Tourists are loving taking pictures of the three Freds - the world's most famous Stone Age man on the world's most famous Stone Age monument," he added.

A spokeswoman for English Heritage, which run the 5,000-year-old site, said: "We are disappointed that this protest group has chosen Stonehenge to make their protest.

"We feel it disrespects the monument and there is potential for the stones to be damaged."

The protesters are Richard West, 40, of Ottery St Mary in Devon, David White, 29, from Southampton, and Jolly Stanesbury, 36, from Ivybridge, Devon, Fathers 4 Justice said.