Eastbourne MP Stephen Lloyd has warned other MPs and peers of the rising number of RE teachers with no qualifications in the subject.
Mr Lloyd says children taught RE by teachers that have no RE qualification themselves could be seriously counterproductive.
The local MP is currently chairing an inquiry, organised by the All Party Parliamentary Group for Religious Education, on the supply of, and support for, teachers of RE. This came after data showed the subject was often taught by non-specialists.
According to Mr Lloyd, in 2011 the number of teachers with no relevant post-A level qualification in RE was 55 percent, twice as many as those who taught history (27 percent).
Mr Lloyd said, “This inquiry is starting to shed light on some serious shortcomings of our education system in embracing in-depth subject knowledge and understanding.
“We are seeing some telling data which indicates that a lot of RE is being taught by non-specialists, and furthermore the specialists are not there in the schools to deliver the high quality of RE that is needed.
“In our first call for evidence session we have started to piece together hard facts which will allow us to go back to the Secretary of State with a robust report that shows what is really happening to RE at a grass roots level.”
The next and final evidence session will be held at the House of Commons early in 2013, with a final report expected in March.