Spanish banks will have to revalue thousands of houses and commercial premises.
The demand is coming from the EU regulators who are said to be conducting a finance audit to assess the banks’ strength.
The banks have been reluctant to undertake the time-consuming work, fearful also of adding more expense to the multi-billion euro writedowns which have already taken place.
Instead, they have argued that previous valuations from 2012 could just be updated.
But the European Central Bank appears to be pushing for consistent application of the Asset Quality Review across all eurozone states.
Other countries have been asking latitude in the ECB scrutiny, but the issue is particularly sensitive in Spain where banks had huge losses on property.
The cost of the reassessment could cost millions of euros, depending on the size of the portfolios being held.
House prices fell an average 7.8% in the fourth quarter of 2013 compared with a year earlier, according to official figures. The market shows signs of stabilising, prices were still down 1.3% from the prior three months.
