It was another Labour MP that called the 1983 election manifesto "the longest suicide note in history."
It was very left wing and very unpopular leading to the landslide defeat that Labour suffered.
And that was pretty much the end of the Labour Party as being a genuine left wing socialist party lead by idealism and the start of it's conversion into the media-savvy centralist party that we see today.
So a massive defeat of the party followed by Foot's resignation and the party shifting pretty much it's entire direction.
Not a good conclusion to his leadership.
So yes I think that it's a good argument to say that he broke the party and yes I also believe that he was wrong over many things but on the other hand he genuinely believed in those things and refused to shy away from them no matter how unpopular with the British public they evidently were.
So for that he deserves some respect and credit and the disappearance of his type of politician is much missed.