Savers are being urged to check for forgotten Premium Bonds as £44 million worth of prizes are still unclaimed, including two £100,000 windfalls.

Over one-third of the UK population collectively has more than £45 billion invested in Premium Bonds. Every eligible bond is entered into a monthly prize draw and investors forgo interest for the chance to win tax-free prizes.

But Treasury-backed provider NS&I says over 898,000 bonds remain unclaimed, with a total value of more than £44 million (see our Premium Bonds guide to see if they're really worth it, and our Top Savings guide for the best deals).

The two largest prizes where no one has come forward are both worth £100,000 and belong to women in London and Manchester, according to NS&I.

The oldest unclaimed prize is worth £25, from a bond bought by a man from South Yorkshire in 1957.

NS&I is nudging bondholders to claim their prizes as many have lost track of their bonds, perhaps as a result of moving house and not updating their address. Many also forget about bonds they were given as children.

There's no time limit for claiming prizes and each one is held until the winner comes forward. To check if you've won, visit the NS&I website or write with your bond number and personal details to Premium Bonds, National Savings and Investments, Glasgow, G58 1SB.

Bond holders can also make themselves easier to find by singing up on the NS&I website. They can opt to have any cash paid directly into their bank account and be notified of their win by email.