The most capped player in rugby, after making 158 appearances for Wales and 12 for the Lions, joined French club Toulon in July on a short-term contract which ended in November.

He had announced his retirement from international rugby in May.

"I was diagnosed with atrial fibrillation," Jones told The Telegraph. "It was discovered when I underwent a full medical check, which included an ECG test, when I joined Toulon in July.

"There is a lot of talk about welfare in rugby at the minute, but does that cover everything? Is it just things that we can afford?

"Surely, the sport has come on to the point where players should be screened more often, especially at a time when the demands in the game are growing."

Jones said he would be forever grateful to Toulon.

"Had they not offered me a contract, I may never have known about the heart condition," he added.

"The cardiac doctor picked it up straight away. My heartbeat was like a galloping horse with six legs. It was all over the shop."

Jones said he took medical advice before deciding he would go ahead and play for the French side.

"It might seem a selfish decision given that I have three young daughters, but I needed to take the opportunity," he added.

"It was only going to be for four months, and it gave me an opportunity to experience and get perspective on my career and life."