Paint on Wet Plaster

There will be no easy way out of this unfortunately, with the plaster still being wet then the coat of paint would not of absorbed into or adhered to the new plaster sufficiently. Basically it will just sit on the plaster instead. My advice would be to let the ceiling dry out completely, a de-humidifier can speed up the process and then once dry ; scrape away all peeling/blistering paint carefully without scoring the new plaster work. Once all scraped back to a solid edge, a fine sanding to the edges of paint will be needed with say, a 150 grit sandpaper or above. This will smooth out the edges preventing them to show through any further coatings of paint. I hope this helps! Luke.

Unfortunately, the paint needs to all come off. Whilst the paint is on top of the plaster it will be acting as a barrier, so the paint will dry but the plaster wont. You will need a dehumidifer to dry it out, once the paint starts drying, it will start peeling and cracking, so you should be able to carefully scrape it off, just be careful not to damage the plaster. And have a firm word with your labourer. Hope you get your issue resolved. Antony