Hundreds of people were voting every minute

Choirs were invited to upload videos of themselves to a website, in a contest alongside the TV talent search for a new Joseph for the West End musical.

People could then rate the choirs online. But there have been complaints about problems with the system, which even had to be suspended for a time.

The BBC has accused some of unfairly trying to boost their choir's chances.

When it reinstated the voting system last Monday, it then insisted people must register to take part.

Explaining this, the programme makers said they had been "amazed by the high levels of rating and the lengths that people will take to improve their choir's ranking".

"Asking you to login and verify your e-mail address acts as an extra deterrent for those trying to break the rules of the competition."

Repeat votes

Schools were ranked on the average rating they got, from five for excellent to one for poor - not simply how many votes they picked up.

Some people might have misunderstood what they had to do.

"When you rate, you need only click on one multicoloured coat," the website explained.

"So, for example, if you wish to rate the choir a four, you click on the fourth coat along in the row. You should not click coats one, two, three and four."

But there have also been claims that people not only repeatedly gave their own choir the highest rating, but also repeatedly gave a low rating to competitors.

In their "frequently asked questions", the producers said it had been "far more popular than we anticipated", with hundreds of votes per minute straining the database.

In answer to the question, How come I can vote more than once? they say: "We identify voters via a bunch of different measures. Some of these measures take place after you've voted.

"Periodically, we sweep the database to remove votes for the same choir that we believe come from the same person.

"This system isn't perfect, but we have gone to considerable lengths to ensure it is a fair as possible and we believe it is generating accurate results."

Respect

In recent weeks the media regulator Ofcom has begun an inquiry into premium-rate phone lines on TV contests following allegations that some shows have misled callers.

Ofcom has had two complaints about the Joseph choirs competition but as websites are outside its purview it had referred them back to the BBC.

In online forums, comments include: "My respect for the BBC has plummeted beyond belief!" and "The whole thing has been one disaster after another, only hope they apologise on the TV show to the thousands of kids who feel let down."

A BBC spokesperson said that as well as increasing the website's capacity to cope with the huge amount of hits it was getting, the deadline had been extended - it ended at 1500BST on Friday 25 May.

"Extras measures were also added on the website including a clarification of how to rate the choirs and a registration system to assist in managing the process.

"Once the verification process has been completed the top twenty, who go forward for judging by the panel, will be announced on Thursday 31 May."

Joseph was written as a school musical and remains enormously popular with children.