Nuisance calls: Direct Marketing Association on TPS service
3 September 2013 Last updated at 14:43 BST
Rogue companies "willing to ignore the legislation" are to blame for many nuisance calls, said John Mitchison of the Direct Marketing Association.
He said people who registered with the Telephone Preference Service (TPS) should not receive sales calls within 28 days, and he called for more enforcement.
Simon Entwisle from the Office of the Information Commissioner, said there was also a "blurring of what counts for consent" for those signing up for TPS, but later appearing to agree for calls to be made.
He said fines had been issued, but the enforcers also had to prove "substantial damage or distress, and that's a problem for us".
They spoke as the Culture Select Committee took evidence on nuisance calls on Tuesday, including from Mr Mitchison.