NS&I blamed the shake-up in payouts on falling interest rates. Bondholders'chances of winning stay the same, but they will be less likely to win a sizeable sum.
NS&I said that from the April prize draw onwards, one of the two monthly premium bond jackpot prizes of £1m would be replaced by "a wider mix of prizes" and a new £25 prize would be brought in. Until now, the smallest amount you could win was £50.
The premium bond "prize fund rate" - the proportion of the total amount invested paid out - will be slashed from 1.8% to 1% a year. However, the odds of winning with each £1 bond number will remain unchanged at 36,000 to 1. This means someone with the maximum £30,000 invested can, "with average luck", expect to win 10 prizes a year.
The total value of prizes next month is estimated at £32m - down from £59m this month and £87m in November.
"Replacing one of the £1m jackpot prizes with a wider mix and introducing the new £25 prize category, will help us maintain the frequency of tax-free prizes - something we know is particularly important to premium bond holders," a spokesman said.
guardian.co.uk © Guardian News and Media 2009
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