Which? said that more than half of "nuisance" calls were about services such as personal injury or payment protection insurance (PPI) claims.

BBC: Which? calls for 'nuisance call and text' clampdown

"The original decision of the OFT to investigate the private motor insurance market came after insurer claims that motor insurance premiums had risen by almost 40% to compensate for the increased costs of personal injury claims (whiplash) and other costs including those of credit hire, " said Martin Andrews of the CHO.

BBC: Car insurance facing Competition Commission study