UP to ?1bn in hot money is set to be reclaimed by the Revenue Commissioners as part of its trawl through Irish residents' off-shore bank accounts, opening up "several goldmines" for the hard-pressed national finances.

It emerged last week that the Revenue netted ?105m from just 254 customers of the Bank of Ireland Trust Company in Jersey. This figure is believed to represent a fraction of the money stashed outside the state during the 1970s, '80s and '90s.

The Revenue investigations are proving a massive boon to the state finances. The investigation into the Ansbacher accounts, for example, is raising an average of ?500,000 per case in back-taxes and penalties, bringing in ?39m to date. Many more Ansbacher cases are still to be examined, with 700 "connected entities" to be investigated.

The trawl by the Revenue Commissioners is being extended to tens of thousands of customers with accounts outside the state in 10 top Irish financial institutions. Given the numbers involved, and the ongoing inflow of revenue from separate investigations into bogus non-resident accounts, tax experts predict a conservative windfall for the state of half-a-billion over the next four years.

Labour's finance spokeswoman Joan Burton believes the final take may be higher. "I am very confident of the prospect of half-a-billion being brought in and ultimately it could be as high as ?1bn, " she said.

Burton, a trained accountant, believes money raised from tax evaders was a "significant factor" in the improvement in the public finances towards the end of last year.

"There is a heck of a lot of money out there. Fianna Fáil said there was no pot of gold out there in relation to evaded tax. In fact there are several goldmines and it is ironic that Fianna Fáil are now the political beneficiaries of that."