The rate was cut at noon on Tuesday from 7.75 per cent net to 7.25 per cent, and investors were given less than 24 hours' notice. The rate on investments of pounds 20,000 plus comes down from 8.05 per cent to 7.55 per cent net.
The original rates were available only for a fortnight, and the sudden switch angered investors.
One who applied for pounds 20,000 of bonds and missed the noon Tuesday deadline accused the Government and National Savings of 'sharp practice' in advertising the bond last weekend and then announcing the rate cut on Tuesday.
'This is like a supermarket changing its prices after I take something off the shelf and before I get to the checkout.'
When First Option's rate was cut, National Savings undertook to apply the original rate to applications received in its Glasgow office by noon on Tuesday. Those who did not make it on time would be contacted by telephone or letter and offered the lower rate.
A spokesman for National Savings said more than half those contacted so far had decided to buy the bond at the lower rate.
Those who have to be contacted by post will have their cheques returned, with an invitation to re-apply at the lower rate.
Peter Richards, of Hastings, posted his application for pounds 4,000 of First Option Bonds on Monday but missed the deadline. He was furious to discover that Freepost is like second class mail.