Former Boris Johnson spokeswoman resigned earlier this month after a clip emerged of a mock press conference held between Downing Street attendees and Ms Stratton. In the video, they laughed at a “fictitious” lockdown party just days after an alleged event occurred.
The Mail on Sunday reports that past and current staff at No. 10 fear more images will come out.
A source told the newspaper that “the worst could be yet to come” in the televised press conference rehearsals that were subsequently dropped.
The source said: “Of course, Allegra is well aware that she was asked more than the one question we’ve all seen.
“She feels very anxious and has totally sunk, she hardly talks to anyone.
“She and her former Downing Street colleagues have become convinced that they know the source of the leak.
“They believe a confidentiality agreement has been violated.
“They live in fear every day that the rest of the questions they ask will come out, because they know they were filmed.
“Any other infraction would be in the public interest, so they feel they can’t stop it.”
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“That was not a failure on the part of the teams involved in the process; they would not be doing their job properly if they had not solved the most difficult questions and had not prepared for them.
“But it just shows what a ridiculous and counterproductive plan it was from the beginning.”
It comes at a turbulent time for the prime minister as he faces the potentially most damaging week of his tenure.
Allegations of parties breaking lockdown during coronavirus restrictions last year have caused a furor.
And Johnson suffered his biggest rebellion earlier this week when nearly 100 conservative backbenchers voted against Covid passes.
The Conservatives also suffered a humiliating defeat in the North Shropshire by-elections on Friday.
In the latest blow to the prime minister’s body, Brexit Minister Lord Frost has resigned citing “concerns about the government’s current direction of travel.”
Express.co.uk has contacted number 10 for comment.