Boris Johnson has told the UK Covid-19 Inquiry he may have only read minutes from the government’s scientific advisory group “once or twice” during the pandemic.

The former prime minister said he was given “summaries” of the discussions but that “in retrospect” it may have been valuable to hear them in full while he was leading the response to the emerging crisis.

The Scientific Advisory Group for Emergencies (Sage), a committee of scientists responsible for advising ministers on Covid, met hundreds of times.

Asked whether he ever read the minutes as he gave evidence on Wednesday, the former prime minister said: “I think I did once or twice look at the – maybe more than that – looked at what Sage had actually said and Sage certainly produced a lot of documentation.

“But I think that the CSA (chief scientific adviser) and CMO (chief medical officer) did an outstanding job of leading Sage and distilling their views and conveying them to me.”

He added that “in retrospect it may have been valuable to hear the Sage conversation unpasteurised itself, but I was more than content with the very clear summaries that I was getting from the CSA and the CMO”.

Lead counsel Hugo Keith KC asked: “Did you not think of looking at the scientific horse in the mouth and seeing what was actually said by the government’s primary scientific advisory committee on these issues when you, as now appears to be the case, you became engaged particularly in the debate of behavioural fatigue?

“Why didn’t you call for the primary material?”

Mr Johnson replied: “I think that’s a good question. I was very, very much impressed by and dependent on the CMO and the CSA, both of whom are outstanding experts in their field and it felt to me that I couldn’t do better than that.”

The former prime minister began the first of two days of questioning before Baroness Heather Hallett’s inquiry by apologising to victims of the pandemic.

Asked to what extent he accepts personal responsibility for the mistakes he admits were “unquestionably” made by his government in its response to Covid, he said: “I take personal responsibility for all the decisions that we made.”