Dominic Cummings said that Downing Street's handling of the fallout from his trip to Barnard Castle was an "absolute car crash" and "did cause a lot of people pain".
He was quizzed on the high-profile controversy and the impact it had on confidence in the Government during his appearance at the Covid inquiry.
He said: "It was certainly a disaster, the whole handling of the situation. But there were other factors involved with it all as well - testing and PPE and many other things were all going haywire at the time."
He said it was "completely reasonable" for security reasons to move his family out of his house, but on the Barnard Castle revelations he said the way it was "handled it was an absolute car crash and disaster and did cause a lot of people pain".
But he added: "In terms of my actual actions in going north and then coming back down I acted entirely reasonably and legally and did not break any rules."
Earlier he told the inquiry vulnerable groups such as family violence victims and children in care were "appallingly neglected" during the pandemic.
WhatsApp messages showed how Mr Cummings had texted the then-Prime Minister to say that Matt Hancock, who was Health Secretary at the time, had "lied his way through this and killed people'.Meanwhile, Boris Johnson argued that the government should let older people get coronavirus to protect the rest of society from the damaging impact of a lockdown, the inquiry heard earlier.
