Kvyat was a lap down after an electronics issue at the start of the race and attempted to un-lap himself on Magnussen after the Renault driver ran wide at Tabac. The two made light contact on more than one occasion through the Swimming Pool complex before Kvyat tried to pass on the inside of Rascasse, causing a collision.
With Kvyat admitting he "didn't really care at that point about this incident because my race was ruined anyway", Magnussen was critical of the Russian.
"We had a good start to the race and made a really good strategic call to change to the intermediate tyres just after the safety car," Magnussen said. "We were the only ones to do it so early and it was the right decision. We were in a good position as a lot of people were still to pit and we gained a lot of places.
"Unfortunately, Kvyat just lost his mind and crashed into me and that was effectively the end of my race. We did continue and made an early change to slicks as we had nothing to lose, but ultimately I hit the wall and damaged the front wing.
"We were several laps down at that point and the car had been in the wars so it was safer to retire. It’s a shame we didn’t have a good weekend as we were very optimistic for the race."
However, Magnussen admits the Renault power unit - which he ran in Monaco - should deliver more of a performance benefit in Canada than it did last weekend.
"Now we have to shift our focus to Canada and have a better weekend there. Montréal should be a stronger track for us and should play to the strengths of the updates for the car."