The report, published by the Religious Education Council and the National Association of Teachers of RE (NATRE), suggests this is likely to be fuelled by a range of factors.
One possible reason is the fact that RE is not included in the English Baccalaureate - a school performance measure that recognises youngsters who studied a group of academic subjects.
Freedom of Information requests asked for the number of hours of RE each secondary school in England taught to each year group - from Year 7 to Year 11.
For each year group, the proportion of schools teaching no hours in 2015 was around one in four, the report calculates, with the highest proportion being around 28 per cent for Year 11.
Graham Nicholls director of church network charity Affinity told Premier the government should ensure RE teaching legislation is being carried out "by competent teachers trained in the basics of the major world religions but also in the essentials of philosophy and apologetics".
But Geoff Barton, general secretary of the Association of School and College Leaders, said schools may be teaching the subject in different ways, rather than through specific RE lessons. He used citizenship classes as an example.
Nicholls added that the Church can also have a role to play in the situation.
He told Premier: "This does present an opportunity for churches that can often help schools by providing the Christian and ethical elements in the teaching programme."
"There are plenty of excellent materials available for teaching about the Christian faith and also about Christian views on sexual ethics and beginning and end of life issues.
We encourage churches to contact their local schools and offer to assist in this way."
The survey also found differences between types of schools - with 96 per cent of faith schools saying they offer the subject to all 14 to 16-year-olds, compared with 73 per cent of academies.
A Department for Education spokesman said the government "firmly believes in the importance of religious education" and insisted that it's required for all state-funded schools at all key stages.
However, the spokesman added: "It is up to schools to decide how to offer RE, whether it is through classes in the subject, or alongside other topics."