The scheme, started as a result of a directive from Northamptonshire County Council, has been formally in force at schools since April.

It means that many children under the age of consent can access condoms and the morning-after pill without parents being informed their child is sexually active.

But the county council said the scheme was a key part in its efforts to halve the rate of teenage pregnancies.

A spokesman said: "Parents know that services are available at school, but that they are confidential.

"The parents are not told that their son or daughter has attended the service although young people are encouraged to discuss issues with parents when appropriate."

Teenage pregnancies in the county have fallen by 16 per cent between 1998 and 2006 although latest figures suggest they still number about 500 per year.

In order to try to reduce that figure, all the 38 secondary schools under the county council now have access to a full range of health advice and information from their school nursing service.

They provide a confidential service which fields pupils' questions about their health problems and when necessary provides them with contraception, including emergency contraception and condoms.

Governors and parents are consulted about the services, which are developed once agreement with them is reached.

Karen Popely, the secretary of the Northamptonshire Federation of Parent Teacher Associations, who has three teenage children, said: "I have a 16-year-old daughter so I know this is a very emotive subject.

"You would hope that your teenager would talk to you about this sort of thing and you could help them through it.

"There may also be issues where family background plays a part in what is being given out, like a history of deep vein thrombosis which could conflict with taking the pill.

"But in the end I would not like to see these children with no-one to talk to."

Sally Keeble, the Labour MP for Northampton North, said she understood potential concerns by parents but was in favour of the scheme overall.

She said: "It is a difficult issue. It is very much preferable if the parent is fully involved and I'm sure the schools see that as well.

"It's really important that some young people have access to advice and appropriate services if they are really in problems."