The government's Money Claim Online small claims service (MCOL) is being overwhelmed by claims for bank charges.
Thousands are suing banks using the Money Claim service
So many people are using the website to reclaim overdraft charges that at times it has slowed almost to a standstill.
The MCOL help-desk blames "very high traffic" and advises callers to log in to the site outside office hours.
A member of staff told the BBC: "We are getting thousands, hundreds of thousands, of cases since the bank charges cases started."
The government's Courts Service does not record what a claim is for.
But with MCOL now handling 600 new cases every day - more than twice the rate seen in 2006 - the bank claims cases appear to be the reason for the recent upsurge.
Kevin Westall, a senior manager in the Courts Service, said extra computer equipment would be installed within two months which would let it handle much more data.
"The numbers of claims have increased recently," he said.
"It's like any web system, such as an internet bank, there will be times when it will be relative easy to get in and times when it will be very busy."
The Financial Ombudsman told the BBC that claimants can use their free-to-use complaints service, see the link on the right hand side of the page for more details.
The flood of claims against banks is also placing an increasing burden on the county courts around the country, where claims are heard if the banks choose to defend them.
"They are increasing in number all the time," said an official at Southend county court.
"All courts are being inundated with them."
Some courts, such as Southend, have adopted a strategy of block booking claims for a particular day so they can all be dealt with at once.
But practice varies around the country.
Some judges will award judgement to a claimant even before a hearing is arranged if they think the banks will not turn up.
Meanwhile a Judge in Hull, as revealed exclusively by the BBC News website, has taken the opposite tack and is threatening to strike out 20 claims on the grounds that they have no chance of winning.
A number of judges around the country have become increasingly annoyed at the tactics used by the banks.
Once the legal procedure has been started by a claimant, the banks typically tend to settle claims just before the hearing, or on the day of the hearing itself, or simply fail to turn up in court at all to substantiate their written defences.
Judge Stephen Gerlis, who speaks for county court judges in the London area, told the BBC's Money Box programme last week that the legal system had no way of dealing with this "mass litigation".
He pointed out that the banks could not be forced into court to defend themselves if they agreed to settle.
Writing for the Times Online, he added: "There has been nothing like it in the history of civil litigation" and described the present situation as "bizarre".
Judge Gerlis called for a change in the law so that the judicial authorities could have a mechanism to drag the matter into a senior court to establish whether or not the banks' overdraft charges are illegal or not.