A rush of savers seeking 'safe' accounts amid the uncertain economy has caused NS-amp;I (National Savings and Investments) to breach its target for how much money it is allowed to raise.
The Treasury-backed body said it overshot its target for net financing - the amount of money left over for the Government after withdrawals and interest payouts - by £18m in the year 2011-12.
This was due to a 'small number' of customers placing large amounts in accounts which guarantee up to £2m, since November, while people had not withdrawn their money as expected.
Unlike banks and building societies, which are covered by a scheme to compensate customers for up to £85,000 if they go under, NS-amp;I is able to guarantee 100% of deposits because it is backed by the Government.
A spokesman for the group said the global instability and the problems in the eurozone were a "key driver" in people placing large sums into its Direct Saver accounts, in which up to £2m can be placed per person, with no set investment term.
Alongside this, NS-amp;I said it saw a decrease in people withdrawing money across its range.
The group moved to stem the build-up by cutting the interest rate on its Direct Saver accounts from 1.75% to 1.5% in January.
But it still meant that NS-amp;I delivered £4.02bn in net financing for the year 2011-12 despite its target of a maximum of £4bn.
High inflation has meant that under-pressure households have had a tough time trying to find any accounts to give them real returns on their money.