National Savings & Investments (NS&I) is to launch an instant access savings account which savers can operate by phone or via the internet.
The interest rate will be decided closer to the account's launch in March but will be "attractive", NS&I says.
Government-backed NS&I is best known for selling Premium Bonds.
Building societies have complained that savings bodies with a 100% government guarantee - such as NS&I - have been giving them unfair competition.
Societies saw a net outflow of savers funds in each of the nine months to last November.
But Jane Platt, chief executive of NS&I, denied her organisation was taking unfair advantage of its government-backed position.
"Our aim this year is to keep in balance our inflows and outflows of savers money - our net financing target - so when building societies say we are distorting the market I don't recognise that."
