As finance minister Brian Lenihan and his advisers ready plans to pump further capital into the country's biggest banks after their toxic loans go to Nama, more figures are emerging from foreign lenders in Ireland indicating just how much more money the government may need to spend to fix the financial system.

In little over a year, Ulster Bank and Bank of Scotland (Ireland) have received about €3.7 bn of capital from their parent companies. Documents just made available at the Companies Registration Office show Ulster Bank got another capital boost from its British owner, the Royal Bank of Scotland Group (RBS), in November.

When the latest €175m injection is included in the various tranches of capital it has received in the past year, Ulster has swallowed nearly €2.3bn to shore up its capital base. Over at Bank of Scotland Ireland (BoSI), now owned by Lloyds Banking Group, around €1.4bn in capital has been received so far to offset impairments on its €32bn Irish loan book.

A simple addition of Ulster's loan book with BoSI's shows a greater amount of capital has gone in to those banks even though combined they would still be smaller than either AIB or Bank of Ireland.

AIB and Bank of Ireland so far received €3.5bn each from the state. Anglo Irish Bank, which has a slightly smaller loan book than a combined Ulster Bank/BoSI, required a €4bn top-up from the Exchequer last May.

And it may not be the last capital that either Ulster or Bank of Scotland need to shore them up against future losses. RBS, which is 84%-owned by the UK government, has warned that loan impairment charges at Ulster Bank will continue to be high in 2010 as property prices continue to slide and the economy shows little sign of growth until later in the year. That view was echoed in comments by Lloyds Banking Group.

Analysts said there are several reasons the foreign banks, not just RBS and Lloyds but also National Irish Bank's owner Danske, have been swift to recognise loan impairments, and consequently provide capital more quickly, in Ireland.

While the €2.3bn of capital pumped into Ulster seems large in comparison to what has already gone into the Irish banks, the Royal Bank of Scotland needed a stg£25.5bn state rescue to deal with the huge amounts of toxic products on its books and the fallout from its ill-fated takeover of ABN Amro. Lloyds, meanwhile, has been focussing on raising cash to avoid the British government increasing its hold over it and the fallout from its acquisition of HBOS in 2008.

Also, both banks increased their exposure to Ireland, and property developers, later into the property boom than other lenders, so they are likely to suffer greater losses on those loan portfolios.

For RBS, it will also begin to recognise losses quickly on loans going into the UK's Asset Protection Scheme, a form of state insurance for the bank. Among the Irish assets going into APS are thousands of mortgages sold by Ulster Bank's First Active subsidiary, according to documents published on the British Treasury department's website. Ulster Bank also says it wants to sell some of its development loans to Nama, the only foreign lender so far to publicly declare its interest in joining. Whether it will actually happen or not is another question.

Lenihan wants to finalise the banks' capital requirements by the end of the first quarter. As probably the only source of the capital, the Department of Finance has not given any estimate for how much it reckons the three banks will need as loans finally move into Nama.

Analysts at investment bank Barclays Capital this week placed AIB and Bank of Ireland on their "Too Big To Fail" list. Barclays said AIB would need to raise 603% of its market value and Bank of Ireland 348% to generate enough capital protect against crippling losses.

The Barclays report didn't give an estimate for how much Anglo Irish might need from the state (its only source of capital). The two building societies, EBS and Irish Nationwide, will also require as much as €2.4bn in taxpayers' money to prop them up post-Nama.

With the transfer of the first loans to Nama now postponed to next month at the earliest it could be that Ulster Bank and Bank of Scotland (Ireland) receive additional funds before the Irish banks receive any more.