Leeds Building Society has increased the maximum balance on its Leeds Reward Bond to £10,000, twice the original balance.
The building society has decided to extend the balance as a result of extra funding and feedback from its members.
However, the building society has stressed that it does not know how long the bond will be available for due to its popularity.
A spokesperson for Leeds Building Society said: "Clearly customers are attracted to the five per cent guaranteed return and, even though we have obtained more funds, it is impossible to know how long we can keep the product available given the current level of demand."
The balance for Leeds Reward Bond joint account is now £20,000.
Leeds also launched its new passbook account for pensioners earlier this month. Called the Flexible Freedom Account, it pays 3.4 per cent to account holders who have their pension paid directly into their account and who want a monthly income.
It also guarantees to pay a base rate of minus one per cent until the end of 2010.To read more about Savings, click here.
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