"Religious Trends is a book of statistics with no real interpretation in there and no commentary on the numbers, but unfortunately the press have picked that up and put two sets of numbers together," she said.
"I have been speaking with Lynda," Ms Hewitt continued. "The church statistics were looking at only Sunday attendance - and I completely agree with Lynda that it's missing out those who attend less frequently than once a week, because increasing numbers are attending midweek and are attending less traditional forms of church. I agree all those things are missing."
The statistics in the latest edition of Religious Trends were put together under the guidance of former head of Christian Research, Peter Brierley, before his departure from the think tank last year. Ms Hewitt said that Christian Research would not be making any more forecasts, but rather shift the focus of its research into present attendance patterns and use that to "build bridges" with non-churchgoers.
"It's always dangerous forecasting to 2050 and I don't think you can reliably do it. Nobody can predict what the world is going to look like in 40 years time. It's just that if present trends continue this is what we are facing. The church needs to change and look at where it is growing, and learn from best practice. And there are all sorts of signs of growth."
New initiatives and a good research department were helping the Church of England to buck the trend of decline quite well, but the other denominations are "falling much, much faster", she warned.
"There is no doubting that the church is declining. And as much as Lynda Barley will point to the positive news - Back to Church Sunday, Fresh Expressions - the overall picture is decline," she said.
"The church needs to change and just adapt more to what's going on and be more sensitive to what's going on in the culture."
Ms Hewitt said she agreed "absolutely" with the title of an article in today's Telegraph, "The Church isn't dying ... but it needs to evolve".
The church "needs to evolve and where it is evolving it is growing", she said. "If it doesn't evolve then those trends that were predicted in the book of stats may well happen. We hope that they don't."
Responding to Christian Research's statistics, Rev David Phillips of Church Society told Premier Christian Radio that there was "very clearly a loss of confidence in the good news about Christ, that He is the Son of God and that He is the only way that we can be right with God".
"I think that we need to regain that confidence. And there is evidence, it seems to me, that churches that are not ashamed of the Gospel are the ones that are most likely to be growing," he added.
