Callers to premium-rate phone competitions on the GMTV breakfast show have been defrauded out of millions of pounds, a BBC investigation has found.
Panorama found that for the past four years, a company working for GMTV had been finalising shortlists of potential winners "long before" lines closed.
GMTV has suspended all phone-in quizzes but said it was confident it had not breached regulators' codes.
The phone operator, Opera Interactive Technology, denied any wrongdoing.
Panorama said tens of thousands of callers had been charged £1.80 to enter competitions on GMTV - but as many as half had no chance of winning.
The programme estimated that since 2003, callers had wasted a total of £45,000 a day - or £10m a year - entering the competitions.
INVESTIGATION IN NUMBERS
£1.80 - cost to enter competition
£45,000 - estimated amount wasted on phone-ins each day
£10m - estimated amount wasted on phone-ins each year
4 - number of years alleged fraud has been happening
Source: Panorama, BBC
GMTV presenters Penny Smith and John Stapleton read out a statement to viewers on Monday.
"GMTV knew nothing of this and is shocked to hear of these allegations," they said.
"We are investigating further but do anticipate bringing our competitions back as soon as possible."
GMTV added that its competitions were being run in accordance with the codes of broadcasting regulator Ofcom and premium rate phone line watchdog Icstis.
Icstis said it had formally written to Panorama to request a copy of the programme's evidence, which it would use to decide whether to launch an investigation into the "serious allegations".
The watchdog also said it would contact GMTV and Opera about the accusations.
Panorama also alleged Opera sales director Mark Nuttall had discovered what was going on in 2003 and sent an e-mail to staff, saying: "Make sure they never find out you are picking the winners early."
Panorama put its allegations to Opera, which says it has "removed relevant staff from normal duties with regard to GMTV competitions pending further investigation".
Mr Nuttall has also denied any knowledge of the early picking of winners or that he tried to cover it up.
In a statement, Opera said it had taken steps to improve its procedures "earlier this year".
"All competition contestant entries throughout the entire competition period are now considered equally and fairly," it said.
GMTV has also conducted an independent review, through Deloitte, and said it was "confident" that "no finalists are being selected before lines closed".
Panorama said Ofcom has launched a formal investigation following a complaint against GMTV and Opera. But Ofcom has not confirmed that it is related to the same issue.
Blue Peter claims
The claims made by Panorama are the latest in a series of allegations concerning the use of premium-rate phone lines by TV companies.
The BBC programme also explores similar controversies over a competition run on the Richard and Judy Show and Blue Peter.
Blue Peter recently apologised because a member of the show's production team asked a girl visiting the studio to pose as the winning contestant in a phone-in competition because of a "technical problem".
Panorama claims the show's editor Richard Marson commended the researcher for their initiative, despite having rebuked them shortly after the show came off the air.
The BBC denies the allegation, and says Mr Marson had merely acknowledged during a team meeting that the mistake "was not made with malicious intent".
Panorama: TV's Dirty Secrets can be seen on BBC One at 2030 BST on Monday 23 April