Jones underwent the same routine medical testing as all replacement players joining the tour and it led to the team's medical staff requesting a further examination by an independent neurosurgeon.
This was due to a concern over the player's recent medical history that included two significant knocks to the head while playing for his country on their recent tour to North America.
On the advice of the neurosurgeon, it was determined that it was not safe for Jones to undertake any physical contact for a mandatory three weeks. This is in line with IRB Regulation 10.1 on concussion.
It is anticipated that Jones will fly out of Cape Town today (Friday, June 12). Head coach Ian McGeechan has stated that at this stage no further replacement player will be required.
"I am very disappointed that on medical grounds I have been told that I am not currently fit enough to play an active role on the tour," said Jones, who featured as a replacement when the Lions toured New Zealand four years ago.
"I was looking forward to getting involved with the rest of the lads but I guess it wasn't meant to be. It has been an up and down year for me in many ways.
"I feel okay at present but obviously I have to listen to the neurosurgeon's advice in terms of my health, and to ensure I make a full recovery."