Cash inflows to NS&I fell in the year leading up to March, reaching a total of £15.3 billion, according to new statistics.
This compared to the £18.1 billion which was provided to the government-backed savings group in the 12 months to March 2010.
The 2009 figure was also substantially higher, standing at £26 billion.
Citing some of the factors behind this drop in cash inflows, the body noted it had to withdraw two inflation-linked certificates in order to avoid exceeding its finance target.
However, the group's inflow prospects for this year are looking stronger, with a higher financing target being set by the Government and the reintroduction of one of its inflation-linked products.
The NS&I financing target will now stand at a figure of £2 billion.
Demand for the new inflation-linked certificate is set to be closely monitored by the group, according to its chief executive, Jane Platt.