"Though having played in 2005, it is still a huge goal of mine to be part of a winning Lions tour," said Lewsey, who called time on a hugely successful England career with immediate effect.
"Therefore, my decision is also made in that I believe performing well in a successful club team week in and week out gives me the best chance possible of being selected for next year's Lions Tour. "
Lewsey, who started all three Tests for the Lions against New Zealand three years ago, won a total of 55 caps for England and was part of the 2003 World Cup winning XV in Sydney.
His final appearance in national colours came in the World Cup semi-final win over France last year, when he scored the match-winning try in Paris.
Despite not featuring since that game in October 2007, Lewsey was named as a member of Martin Johnson's Elite Player Squad for the current season.
"I spoke with Martin on the phone earlier this week and, as he didn't consider me to be an integral part of his immediate team moving forward, I have decided that I would be better served committing myself entirely to my club, London Wasps," added the 32-year-old.
"After 55 caps, many training sessions and a vast amount of laughter I'd like to thank all the coaches, medics and especially the players that have made my England career so memorable over the past ten years. Playing, but more importantly winning, for your country is the most special feeling one can achieve.
"My last game for England was the semi-final of the World Cup in Paris last year and, although I would have liked to have contributed since, scoring the game's only try was in hindsight a fitting moment to last wear a national jersey."
Wasps currently lie ninth in the Guinness Premiership, 15 points behind joint leaders London Irish and Gloucester, and Lewsey is now keen to focus on helping the reigning English champions climb back up the table.
"It is my belief that last year's Guinness Premiership title was not won during the play-off period at the end of the season, but during the Six Nations in which we did not lose a game and put ourselves into a position in the league from which we could launch a title bid.
"With so many of our players already away on international duty, being away with the national squad from Sunday to Wednesday each week has been enormously disruptive on the club's and my own individual preparation. I feel that I can have a more positive influence at Wasps throughout this important time if I am consistently here and have made the decision to focus my efforts solely on the club's campaigns.
"On a personal note, over the past two seasons, though not being selected internationally, my club coaches have been very happy with my form and attitude. It is a very exciting time for Wasps and while many onlookers may have written us off, our challenge is to improve on our poor start to the season, building on recent wins to generate momentum and push to challenge for yet more silverware."