The main deadline for applications is 15 January

The deadline for applications for Oxford and Cambridge and medical and veterinary schools is 15 October.

But some schools and universities say they are experiencing problems with the system.

Ucas, the body which co-ordinates the applications, says no student will be disadvantaged.

Joss Buchanan, head of sixth form at King Williams College on the Isle of Man, told the BBC news website the situation had been "chaotic".

The school had not been able to send in online applications until 22 September because the system kept crashing, and pupils had not received letters acknowledging their applications or giving them their Ucas password, which would enable them to track the progress of their applications online.

"It's infuriating," said Mr Buchanan. "Every school will be in the same position. It's the children and the parents who are suffering. This is very important in their lives and they are very stressed."

He said Ucas had not kept schools informed.

'Minimise disruption'

It is understood that universities which were expecting to receive paper copies of applications were sent incomplete versions which then had to be returned.

They are now accessing the applications online.

Newcastle University has a big medical school for which applications are due in now.

A spokesperson said: "We are aware that there is a problem at the moment. We are working on ways around this so as to minimise any disruption to candidates.

Oxford University said its admissions officers had "not received everything as they would have expected" from Ucas.

"But they can access the information online through a secure server, so they are working with it," a spokeswoman said.

She said it was too early to say whether the situation would become a real problem.

We are conscious that there have been some glitches but no one will be disadvantaged Ucas

A spokeswoman for Ucas said large numbers of applications were coming in to meet the deadline - which was being extended until Monday - and that she was not aware of any problems with the incoming applications.

"We are conscious that there have been some glitches but no one will be disadvantaged.

"Universities are able to view all applications via the web and while there were some early compatibility issues these have now been resolved and the system appears to be working well," she said.

"There have been issues with the paper copy forms that many universities and colleges still require. This is now being rectified.

"We would like to point out that no applicants will be disadvantaged by this. It is a condition of Ucas membership that all applications received before the deadline are given equal treatment."