Deputy Labour leader Ms Rayner, who has been subjected to horrific online abuse including death threats herself, said she was worried about the targeting of the TV stars.
“It hurts when people think that they can call you thick and all of those things,” Ms Rayner said, reflecting on the abuse she has suffered.
“I’ve seen it with what was happening with Philip Schofield and Holly just recently.
“I’ve been worried about them because even though they are celebrities… they are human beings and I just think ‘wow’.
“The way in which the online attack on them, as a human being to have that, I just think is really damaging.”
At a fringe event at the Labour Party conference Ms Rayner said the scale of online abuse meant it was important for Parliament to legislate.
Her message to social media firms was “it’s your gaff, sort it out, you have responsibility to do that” but self-regulation had so far failed.
“They’ve tried to self-regulate, they’ve tried to say ‘we’ll look after you’. They haven’t, they’ve not been able to do it and now it’s time for us to legislate.”
Schofield and Willoughby attended the lying in state to film a segment for their ITV morning show without taking part in the public queue.
The pair acknowledged the backlash but stressed they had “respected” the rules set for the media.