How to paint over a bad surface?

Hi All,

Does anyone know a way round this? Matt paint has been used over the top of silk paint, which may have been used over the top of bathroom paint, and the result (unsurprisingly) is a crazed and cracked surface. Is there any kind of undercoat or something that could be put on top of this before repainting? We are trying to avoid scraping all the walls. Any ideas that don't take hours of work or cost a huge amount would be welcome.

Thanks in advance.