London - Oasis was thrown into a new crisis last night when another of its members left to spend more time with his family. Paul McGuigan, the bass player, used a fax to tell the rest of the band he was leaving. The blow comes less than a fortnight after the other guitarist, Paul "Bonehead" Arthurs, went his own way - and at a time when the group's reputation is in decline, a fourth album is unfinished and a world tour is looming.