Ant McPartlin and Declan Donnelly have lost around £2.5 million in just one year, according to company filings.
One of their main businesses, Hurley Promotions, dropped from £5.2 million to £2.6 million within a year.
The company was set up in 2013 in order to take care of the Saturday Night Takeaway hosts' earnings.
It is believed that the money was lost after the collapse of a luxury apartment development in the Algarve.
They both invested in development, called The Keys.
Mirror have contacted Ant and Dec's representative for comment.
Along with Hurley Promotions, the duo also have Mitre Holdings - which was named after the pub in Byker Grove, the BBC programme they both starred in.
Despite losing millions of pounds, the duo have been thriving in the television industry with their endless hosting gigs.
Not only do they front Saturday Night Takeaway, but they also returned as the hosts of Britain's Got Talent.
Fans got to watch them present the hit show I'm A Celebrity... Get Me Out Of Here! recently, which was filmed in Wales.
It was also confirmed that their show, Ant and Dec's Limitless Win, has been renewed for a second series
The ITV game show - hosted by the fan-favourite duo - has come under fire by some viewers for being too difficult to understand whilst others have called it "slow-moving".
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Before the final episode aired last month, ITV bosses confirmed the show - which sees contestants climb a money ladder to win a limitless jackpot - has been recommissioned for another series.
Confirming the news, the presenting duo said they were ready for "another series of nail-biting drama, jeopardy and tension".
"We are thrilled that Limitless Win has been a hit with the viewers and is coming back for more. We're beyond excited to be able do it all over again and we can’t wait to find new contestants to play the first TV show with a limitless jackpot!" Ant said.
Whilst Dec added: "We’re already preparing ourselves for another series of nail-biting drama, jeopardy and tension as we present more questions you can’t help but Google! We’re expecting more, and higher, dizzying climbs up the Limitless money ladder. We can’t wait."
Ant and Dec are also thought to have signed a three-year deal with ITV deal worth around £40 million.
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