AIB and Bank of Ireland together provided an interbank deposit of €4bn to Anglo Irish as recently as December, according to documents seen by the Sunday Tribune. The two banks last week refused to comment on whether they are still providing inter-bank deposits on this scale to the now nationalised lender.

The two banks, Ireland's biggest lenders, provided the funding from 19 December onwards and the sum subsequently grew to €6bn, according to documents prepared at Anglo Irish. The subject of inter-bank lending and retail deposits is expected to be surface when AIB presents its annual results tomorrow.

The documents say the deposits "prevent Anglo Irish Bank from having to access emergency funding, which could be materially damaging to the wider Irish banking sector".

AIB said no funding is provided or received by AIB other than through interbank lending facilities. "This is quite normal practice," said a spokesman. BoI refused to comment on its recent interbank activities.