Mr Cummings, chief advisor to Boris Johnson, is being urged to resign in the wake of allegations he infringed rules the government has imposed to stop the spread of coronavirus.
A political campaigning organisation called Led by Donkeys drove to Mr Cummings’ house in a van brandishing a video of Mr Johnson’s speech which urged the public to stay at home.
The protest on Sunday followed the news that Mr Cummings drove to County Durham, where his family lives, despite social distancing rules.
The prime minister offered his “full support” to his chief adviser after the news emerged.
Led by Donkeys also put up a separate installation on Westminster Bridge Road on Friday.
Posting a photo of the billboard, which reads “Stay alert, government incompetence costs lives”, the group said: “When the PM’s top adviser is crisscrossing the country with coronavirus, it’s definitely time to stay alert.”
After reports that Mr Cummings made a second trip to Durham, which he has denied, Downing Street said it would “not waste time” replying to fresh allegations from “campaigning newspapers”.
Speaking outside his London home on Sunday, after one journalist asked if he had been back to Durham in April, Mr Cummings said: “No, I did not.”
Mr Johnson will front Sunday's daily Downing Street press conference, after calls from Labour for him to appear to explain what went on.
While Labour has issued pleas for an urgent inquiry into the allegations, backbench Conservative MPs have demanded Mr Cummings mull over his governmental role.
Additional reporting by Press Association