Interest rates for balances above pounds 25,000, previously pegged at 5.1 per cent, have been increased to 5.2 per cent up to pounds 49,999.
They rise to 5.65 per cent for deposits up to pounds 499,999 and to 6.15 per cent thereafter.
Gina Fusco, a marketing manager at Abbey National, said: 'These improvements demonstrate our strong commitment to the voluntary sector. They further improve what we believe is already one of the most competitive charity accounts on the market.'
Abbey National's new offer mean it now pays the second-highest rates among all societies for deposits above pounds 500,000.
It is beaten only by the tiny Furness Building Society, based in Cumbria, which pays interest of 6.25 per cent on deposits above pounds 100,000.
It also outdoes the Abbey on deposits above pounds 50,000, paying 5.8 per cent.
Furness has 17 branches in Cumbria and offers two machines for instant cash withdrawals.Reuse content