Boris Johnson was interrupted as he apologised for the “suffering” caused by the COVID pandemic.
Four people were subsequently removed from the hearing, where they had been in the public gallery holding up pictures.
Mr Johnson had told the inquiry: “I am deeply sorry for the pain and loss and suffering.”
One protester held up a poster reading: “The dead can’t hear your apologies.”
The former prime minister was speaking on the first day of his appearance at the official COVID inquiry he set up in order to learn the lessons of the pandemic for the future.
He is the inquiry’s most highly anticipated witness.
He follows on from fellow politicians including former health secretary Matt Hancock, former deputy prime minister Dominic Raab and Levelling Up Secretary Michael Gove.
Mr Johnson will be questioned for two days about decisions he made which took the country into three national lockdowns.
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