Fixed-rate savings bonds are usually the preserve of the habitually cautious. But changing expectations about interest rates are bringing this out-of-fashion product back into vogue.

The improving economic outlook and worries over inflation have left economists predicting that the next rate move will be upward.

While this is bad news for overstretched homeowners, it is good news for savers who are already beginning to benefit from a series of new fixed-rate savings bonds paying more than 5 per cent.

National Savings & Investments has also increased its rates today. The return on two, three and five-year bonds has risen by up to 0.4 percentage points. Those with savings of more than £50,000 will now receive 4.55 per cent on three and five-year bonds. More modest balances of between £500 and £20,000 will reap 4.2 per cent.

The sudden glut of attractive rates on the market has prompted some experts to recommend that people weight their portfolios towards longer-term bonds.

Rachel Thrussell, head of savings at Moneyfacts, the price comparison service, says: “The increases are quite substantial. Some have gone up by as much as half a percentage point, certainly a big enough increase to make it worthwhile for savers to review their portfolios.”

Fixed-rate bonds are only one component of Mike and Pauline Green’s savings strategy. The couple, from West Yorkshire, have a two-year bond with Skipton Building Society that pays 4.95 per cent. They took the deal at the beginning of May, and although the rate that Skipton pays on two-year bonds has now increased to 5.01 per cent, they are not too disappointed.

Mrs Green says: “The rate we have is still relatively high. The reason we spread our investments across different asset classes is to minimise the impact if one underperforms slightly.”

The best of the new one-year bonds comes from Birmingham Midshires, at 5.16 per cent. However, some exclusive one-year bonds, such as those aimed at the over-50s or branch users, may pay slightly higher rates.

In the two-year market, Norwich & Peterborough Building Society pays 5.25 per cent on balances of more than £1,000. For those prepared to invest for three years, Heritable Bank offers a market-leading 5.31 per cent, while Bradford & Bingley’s eBond pays 5.25 per cent.

Five-year fixes have little to recommend them. Sue Hannums, of AWD Chase de Vere, the independent financial adviser, says: “The difference between rates on three-year and five-year bonds at present does not really justify locking away money for five years.”

The Portman and West Bromwich building societies and the Royal Bank of Scotland all increased their fixed rates this week. MBNA is the only institution so far to buck the trend by reducing rates on all its bonds by a quarter of a point, down to 4 per cent.

Concerns that the three-year bull run has come to an end make fixes look even more attractive. However, there is always a risk that you may miss out on further rate increases by fixing now.

Given predictions that the Bank of England base rate will increase by a quarter of a percentage point by the end of the year, it would seem prudent to wait for the possibility of further rises in savings rates.

But this is not necessarily the case. Fixed-rate bonds are priced on movements in swap rates, the money markets used by the City. These usually pre-empt changes in the base rate, so predicted interest rate rises will already have been factored in to the new bond rates.