Government officials have estimated that the five Dublin banks will together need an extra €6bn - mostly from extra taxpayer cash and the proceeds of the break-up of AIB - to make good the average 30% discount banks will be paid for their bad commercial property loans, the Sunday Tribune has learned.

The government is hoping that the extra €6bn - on top of the €11bn in public funds it has already committed to AIB, Bank of Ireland, Anglo Irish, Irish Nationwide and AIB - will mean that the final public bill for recapitalising Ireland's banks in this crisis will not exceed €17bn.

That is "in the ballpark", a senior source said.

The government is understood to be following estimates the IMF provided in its report on Ireland published at the end of June. Last week's IMF global report on global banking losses is not believed to have changed significantly estimates for the loan losses of the Irish banks, an IMF spokesman in Washington said on Friday.

The recapitalisation arithmetic means it will make it a racing certainty that AIB will sell its €1.1bn stake in US bank M&T.