The number of teachers training in personal, social, health and economics (PSHE) education has fallen 90 per cent, according to figures released by the education select committee.
After the coalition stopped funding free access to accredited PSHE courses, the numbers in the scheme fell from 1,937 in 2010 to just 175 last year.
Only 141 of that number completed the course, run by the University of Roehampton, which now costs £700.
In an article for The Sunday Times, education secretary Nicky Morgan wrote of complaints from parents who felt their daughters were under pressure to have sex.
She also described plans for “consent classes” to be taught to children as young
The PSHE Association has drafted guidance for the lessons and it is understood the Department for Education (DfE) will include it in the PSHE syllabus.
The association said that while it provided training on “specific aspects” of PSHE education it only had the resources
to train “hundreds”.
A spokesperson said: “This means there are thousands of teachers out there who have not received the necessary training to deliver lessons on issues that are often complex and challenging to teach.”
Lucy Emmerson of the Sex Education Forum said: “What is needed is a commitment to make sex and relationships education (SRE) and PSHE statutory in all schools.
“There is a big difference between the government supporting the new consent guidance, which is essentially optional for schools, and the government guaranteeing that all children and young people receive good quality SRE – which requires a change in legislation and investment in training for teachers.”
Last year, the education select committee called for PSHE and SRE to be made statutory.
Committee member and Labour MP, Pat Glass, has raised concerns about the falling number of teachers trained to deliver the subject.
In a committee session she questioned Ms Morgan’s recent announcement of a £10m fund for “character education” projects.
“That would have trained 14,000 teachers at £700 each on the Roehampton course. In terms of government money . . . £10 million is not a great deal if we are really serious about training teachers.
“One of the consistent pieces of evidence that we have had is that if you are going to deliver this, deliver it well – and the best way of delivering it is by having trained teachers who are experts in PSHE.”
The association’s guidance says: “As part of learning about consent, pupils must learn that the law is clear that sexual activity is illegal for young people under the age of 16.
“We know, however, that some young people are sexually active before 16 and learning about healthy relationships is crucial to keeping them healthy and safe from abuse and exploitation.
“Recognising that some young people will be sexually active before the age of 16 does not equate to encouraging underage sexual activity.”
A DfE spokesperson said: “We want to see all young people leave school prepared for life in modern Britain. This means not only ensuring young people receive a rigorous academic education, but also helping them to develop important personal skills and attributes and develop their emotional wellbeing.
“We are ensuring teachers have high-quality resources and appropriate support and guidance so they can tackle the issues facing young people today. We will also raise the status of PSHE to recognise those schools that are already providing pupils with a well-rounded curriculum, and ensure all parents can be confident their child’s school is providing a curriculum for life.”