The 32-year-old Saracens forward, who began his international career in 2012, missed last year's World Cup because of back surgery but was expected to be involved in the upcoming Six Nations.

"It's been an honour to have represented my country but all good things must come to an end," he said on Instagram.

"The time has come to step away now. There have been lots of highs and lows. Would love to thank everyone who have helped me along the way.

"To my wife @alex_vunipola thank you for taking care of our family and all your support. Words don't do it justice.

"To my parents I'm eternally grateful for all you have sacrificed for me to be here. Malo aupito and Ofa atu. God is good."

Meanwhile, England front-row Ellis Genge is "ready to go" for the Six Nations campaign, according to Bristol boss Pat Lam.

Genge, an England captaincy contender following Owen Farrell's decision to miss the Six Nations, has not played for his club Bristol since early December due to a hamstring injury, but Lam has delivered an encouraging fitness bulletin.

"Ellis has a chance of starting the Six Nations. He is right on track," Lam said.

"He has started running and will probably join us in training next week. The medical team and Ellis have done a great job.

"He looks bigger as well, and one thing you can do when you are injured is get bigger, stronger, faster and more powerful.

"He will not play for us next weekend, and then he is with England so will not be with us for Bath (on January 27).

"I do not know if they would release him for the Bath game because they will be away abroad. That is up to Steve, but he is ready to go for England."

Genge's fellow loosehead props Joe Marler, Bevan Rodd and Val Rapava-Ruskin are also currently on the sidelines.

Sale forward Rodd is out for the rest of this season after undergoing toe surgery and Gloucester's Rapava-Ruskin, who was part of England's World Cup training squad last year, is another long-term absentee following a knee operation.

Marler has an arm injury, the extent of which has not yet been revealed by his club Harlequins.

Quins head coach Danny Wilson said on Tuesday: "Joe is a week-by-week process at the moment to make a full assessment of the time period and the time-frame.

"He is not going to play this weekend – that is pretty clear – but what I can't give is a time-frame. There have been a few twists and turns with it.

"Until we get a full picture and a full time-frame, and we are in that process at the moment, then I can't really tell you a huge amount."