The Office of Fair Trading is to investigate Britain's £780m billboard advertising market.
The consumer watchdog has launched an investigation into the structure and competition within the outdoor advertising sector following concerns raised over potential issues.
Outdoor advertising is highly concentrated in the UK, with only a few key players such as JC Decaux, CBS Outdoor and Clear Channel Outdoor. The sector has a complex structure, with main parties including advertising agencies, specialist buyers of outdoor advertising space, media owners who provide the space and site owners such as local authorities.
The OFT hopes to finalise the initial phase of its study by August, for completion in December.