The London Irish back will move to Franklin's Gardens this summer, with Saints confirming his arrival just a day after landing Newcastle captain Phil Dowson as part of their squad for next season.

Geraghty, 22, is rated among the brightest prospects in English rugby. He made his Test debut against France during the 2007 RBS 6 Nations, and he also briefly appeared this season during England's victory over Italy.

Normally a fly-half or centre, Geraghty joined Irish in 2004, but a move away from the Madejski Stadium has been touted for some time.

He said: "I am delighted to be taking up the new challenge that has been offered to me by Northampton Saints, and to work with the coaching team who I know from my involvement with the England Under-21 team.

"This opportunity will allow me to enjoy being part of the club's future ambitions and also enable me to hopefully force my way back into the England team."

Saints rugby director Jim Mallinder added: "Shane is an exciting, young, English talent and I am delighted that he has signed for us.

"Although he is still young, he has played at all levels of the game, including England internationals and a Heineken Cup semi-final, as well as the Guinness Premiership.

"This experience, existing talent and potential to improve still further make Shane an excellent addition to our squad.

"We want players who can help Northampton Saints achieve our ambitions to become one of the top clubs in England and Europe over the next few years, and Shane is one such player."