I have fixed paint similar to this in my current house. There were large areas where I could peel it off back to the plaster by hand or with a scraper.
Your builder's first coat has failed to adhere to the plaster and now it's peeling off. This could have been caused by:
Painting with full strength paint rather than a mist coat
Painting before the plaster ...
Here's how you get paint to stick to things.
Paint cannot bond to a shiny surface; don't take my word on it, try to paint a mirror and see what happens.
Paint wants to see a surface that looks like Swiss Alps on a microscopic level - lots of jaggies and crevasses for paint to flow into and bond in shear. To human eyes, that doesn't look ...