European Union taxpayers had at least $1.6trn offshore in 2016, with citizens in Cyprus and Malta keeping about 50% of their wealth abroad, according to the European Commission.
According to the report, The offshore holdings of Maltese taxpayers are valued at €5.2bn, estimated at 48% of GDP.
Member States with the largest offshore wealth in GDP terms are Cyprus, Malta, Portugal and Greece, which are consistently above the EU-28 average. In each year the ratio of offshore wealth in these countries is above 20%.
This is against 12% in France, 10% in Germany and nearly 9% in Britain, the three largest countries of the bloc.
Offshore holdings, although in many cases completely legal, could help taxpayers hide taxable money and cut their bills if they stash their savings in low-tax jurisdictions.
Brussels said the $1.3trn held offshore equals nearly 10% of the bloc's output and costs an estimated $50bn a year in lost tax revenue.
"Tax evasion may not be the main and only reason why individuals seek to hide their wealth in offshore accounts. Other motives include the concealment of the proceeds from crime or corruption and the hiding of wealth from public agencies, business associates or family members," the report reads.
Member states with the largest share of offshore wealth are Germany, the UK, France and Italy, contributing to more than 65% of the EU's estimate offshore wealth.
At a global level, the EU estimated that $7.8trn was held offshore in 2016.