National Savings says it has 'fixed' website problems
The government's National Savings & Investments (NS&I) agency believes it has resolved issues causing its website to stop working properly.
A spokesman for NS&I said the website would be monitored over the weekend, but that he hoped "we have fixed the issues".
Members of the public have said the NS&I site failed completely to load on their computers.
NS&I said that the problem, which started on Thursday, was intermittent.
A spokesman apologised for the inconvenience and said NS&I was still trying to determine what caused the technical fault.
He said customers could still make transactions by phoning the NS&I call centre.
NS&I offers government-backed savings accounts and is most famous for selling Premium Bonds.
In November, it announced that it would stop opening new investment and savings accounts over the counter in post offices, in favour of using the internet, mail or phone banking.