Breakfast broadcaster GMTV has dropped the company that provides its phone-in services after a BBC investigation claimed callers were being defrauded.
Panorama said that for the past four years, Opera Interactive Technology had been finalising shortlists of potential winners "long before" lines closed.
Panorama estimated that £10m a year was being spent by callers, but as many as half had no chance of winning.
Earlier, Opera denied the claims and said it would hold an investigation.
GMTV now says it has terminated its contract with the company after its own inquiries revealed "irregularities" in the system the service provider was operating.
Panorama said tens of thousands of callers had been charged £1.80 to enter competitions on GMTV - but winners were shortlisted before lines closed.
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
The programme estimated that since 2003, callers had wasted a total of £45,000 a day - or £10m a year - entering the competitions.
'Shocked and saddened'
In a statement, GMTV apologised to its viewers and said it was "shocked and saddened" by the allegations.
"The first we knew of any problem with our voting system was when we were approached by Panorama some 10 days ago.
"Our contract with Opera makes it quite clear that competition finalists could only be chosen after the lines were closed, giving every viewer an opportunity of winning.
"It is now clear this detailed process was not adhered to by some Opera employees.
"We have therefore terminated our contract with Opera with immediate effect and our competitions will be suspended until further notice."
Opera was unavailable for comment on the GMTV announcement but an earlier statement said the company had recently improved procedures to ensure all contestants were considered "equally and fairly".
Opera had not "benefited financially from any errors in procedure in the past", it said, and had "removed relevant staff from normal duties with regard to GMTV competitions pending further investigation".
The company told Panorama there was "not a shred of truth" in the allegations.
Premium rate phone line watchdog Icstis said it had written to Panorama to request the programme's evidence, which it said 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.
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 competitions 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".