A leaked report reveals that the Church of England may have lost a fifth of its regular worshippers during the pandemic.
Parishes up and down the country moved their services online during the first lockdown in March last year, with the Church for the first time launching an online national Sunday service broadcast live on its website, YouTube and Facebook.
Even though churches in England have been permitted to stay open during the current lockdown, many have chosen to offer online services only because of high Covid-19 numbers.
The Money, People and Buildings report, published in The Sunday Times, was sent to 42 diocesan secretaries this month and expresses concerns that even once churches open fully again, some former worshippers may never return to the pews.
The report also warns of painful cuts on the horizon, with most dioceses planning to "prune" the number of clergy and diocesan staff on the books.
Further doubts are cast on a financial subsidy being given to 5,000 loss-making parishes, while some in the Church expect that reforms will lead to the sale of many vicarages.
Commenting on the likely long-term impact of Covid-19, the report reads: "Online worship will have become a significant part of the mainstream.
"The Church of England could emerge from the pandemic smaller in terms of engagement by at least some measures, but particularly physical attendance.
"This will inevitably have further impact on the sustainability of many local churches."
Even before the pandemic, the Church of England was experiencing a downward trend in attendance.
In 2015, weekly attendance fell below a million for the first time, dropping to 845,000 in 2019 before the outbreak of Covid-19.
The report adds: "There has been some horror expressed at the clergy number reductions announced by a few dioceses, although they are in the context of the consistent decline in clergy numbers over recent decades and the unsustainability of ministry in many parishes."
Anglican priest and broadcaster Giles Fraser said the report "certainly makes for very grim reading".
"There is little doubt that the parish structure, the cornerstone of the English church, is now under threat," he said.
Last summer, the Diocese of Sodor and Man said the financial impact of the pandemic had been "catastrophic" and that it was at risk of running out of money in five years.
It warned that buildings may have to be sold off to plug the "financial black hole" in the diocese.