Nearly three million phone calls - at around £1 a time - were made to the You Say We Pay quiz on Richard and Judy after finalists had already been chosen.

In Deal Or No Deal, presented by Noel Edmonds, Channel 4 allowed a competition to continue for seven weeks after discovering its selection process, which disadvantaged later entrants, was unfair.

The phone-ins on both hit shows raised more than £27 million while there were problems with the way winners were being selected.

In Deal Or No Deal, around £15 million was raised while the competition was run unfairly without Channel 4's knowledge between August 2006 to March this year.

During the period that the broadcaster knew viewers were not being treated equally the competition raised a further £2.1 million. Gross revenue from You Say We Pay between 2001 and 2007 was more than £10 million.

Channel 4 has been instructed to broadcast a summary of Ofcom's findings on three separate occasions.

The fine comprises £1 million for You Say We Pay and £500,000 for Deal Or No Deal. Both quizzes, which used premium-rate numbers, are no longer on air after the broadcaster decided to shut all premium-rate competitions.

Channel 4 said it would like to "apologise once again" to viewers. It announced it was starting legal proceedings to recover costs from Eckoh, the service provider for You Say We Pay.

Collectively, the fine is the second largest imposed by Ofcom following the £2 million sanction against GMTV.