The musician, who is headlining the British Summer Time festival with Dylan in July 2019, said on his Archives website he had "no idea" the announcement was coming and that he was deprived of the opportunity to give his subscribers with first access to pre-sale tickets.
He also criticised the event's sponsor, Barclays, referring to it as a "fossil-fuel-funding entity" and saying it is incompatible with his beliefs regarding climate.
Young, 73, said he was still polishing art for the show's poster and working out the final details of the show to ensure they were "agreeable" to him when someone "jumped the gun" and announced it.
"The tickets were put on sale and the announcement was made, all without my knowledge," he said.
The musician said he was "angry" when it turned out his subscribers wouldn't learn about the show first, nor would they have prime access to pre-sale tickets.
Some fans, he said, felt "confused, resentful, even angry".
As for the event's sponsors, they include Barclaycard, a division of Barclays that provides credit card and payment services.
Barclays appears among several of the world's top banks in a 2018 report by the Rainforest Action Network on fossil fuel funding.
It scored a D+ on tar sands, a D in Arctic oil, and a B- in the coal mining category.
Barclays ranked 12th out of 36 banks listed in the report.
Young said having Barclays as a sponsor "doesn't work" for him.
"I believe in science," he wrote. "I worry about the climate crisis and am deeply concerned about its massive global ramifications and my beautiful grandchildren's future.
"There's no doubt about it – it's been a massive f*** up!"
Young said he and others are "trying to rectify the situation" and said an update regarding the "status" of the Hyde Park show would come soon, adding: "We're sorry for this situation – it is – and shall remain an anomaly."
The Independent has reached out to BST for comment.
To buy tickets to British Summer Time Hyde Park 2019, click here
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies