12 Dec, 14:42
Prop Cian Healy is expected to miss the start of the 2014 RBS 6 Nations after undergoing surgery on his injured ankle on Wednesday.
McNamee is set to be included in Irish coach Mark McDermott's IRB Under-21 World Cup squad, which is announced tomorrow, for the tournament in Argentina next month.
The 20-year-old Northampton-born starlet said: "This really is a dream come true for me. I have supported Saints all my life and watched the club play from the terraces. It is a great opportunity and a great honour to officially become a part of the first team squad."
The 6ft 2in red head made one appearance for the Saints against Bedford in the sixth round of the Powergen Cup this season.
Northampton Academy coach Rob Hunter told the club's website: "Brett has worked incredibly hard to earn this chance. He is extremely professional and has a huge desire to play for Northampton. He plays with heart, is tough and committed. We wish him the best of luck in his professional career both with Saints and Ireland."