Edits made to the Hillsborough disaster page on Wikipedia have been described as an "absolute insult to victims and their families".
Margaret Aspinall, mother of one of the victims said: "It's an absolute insult to the families who are fighting for where we are today and it has to be investigated".
Sheila Coleman from the Hillsborough Justice Campaign added that the distress was compounded by the timing of the revelations.
"That this happens now when the families are immersed in the inquest procedure goes to the heart of why should they trust the establishment," she said.
More top news
In a wide-ranging Peston on Sunday interview, he said Parliament security needs reviewing and the PM's counter-terror strategy is flawed.
The star celebrated his 70th birthday with his family before attending a celebrity-filled bash held in his honour.
Douglas Carswell told ITV's Peston On Sunday he wanted to "support" the government as a "critical friend" but refused to rule out a return.