According to a new data, numbers decreased by 1.6 per cent between 2017 and 2018.
Less than half of English secondary schools now offer Religious Education at GCSE and just 237,862 sat the exam this year.
While all schools have a legal requirement to teach the subject, there are insufficient measures to hold them to account.
Chair of the National Association of Teachers of RE, Ben Wood says Religious Education is often viewed as an irrelevant subject.
"For a lot of schools, there is no real incentive to offer the subject if they don't see it as important. So what we need to look at is how we can make sure RE fits the needs of the students we've got in this country.
"The subject has evolved considerably, I think, over the last 30-40 years and continues to do so."
Entries for GCSE RS in England and Wales peaked in 2011 at 461,795.
Today's figures show a decline in entries of over 42 per cent in eight years.
Wood suggested the government is responsible: "There's a lot of pressures on schools in terms of getting everything into their curriculum. What we're seeing is that a number of subjects are being squeezed out of time. Religious Education is one of them because the government is suggesting that students should see quite a narrow group of subjects. That's the principal reason for this decline."
Wood argues that RE offers valuable life lessons that help young people to grow and understand today's society: "It gives them understanding of the world around them and prepares them to go into that world, both in terms of debating and discussing and learning about matters of importance to religion, but also wider philosophical and ethical questions."
Chief Executive for the Religious Education Council of England and Wales Rudolf, Eliott Lockhart is calling on the government to take action: "Today's figures show the long-term impact in England of reforms introduced when Michael Gove was Secretary of State for Education.
"There are now almost 200,000 fewer key stage 4 pupils studying for a qualification in Religious Studies than there were in 2011. This is particularly distressing given how popular the subject is with pupils and how relevant it is in today's world.
"Last year the independent Commission on Religious Education offered proposals for how to secure the future of religious education that had widespread support from stakeholders across education.
"It is time that the Government engages fully with the recommendations and for it to take action to support high quality religious education for all pupils in all schools."
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