The present invention relates to hair colouring and bleaching compositions comprising i) at least one source of peroxymonocarbonate ions, ii) at least one alkalizing agent, preferably a source of ammonium ions, and iii) at least one radical scavenger, wherein said composition has a pH of up to 9.5, which provide a high level of lift and lightening and the required dye deposition and grey coverage whilst reducing the concentration of peroxide, the ammonia odour and reducing the hair fibre damage.