Maddison and Marriott have been two of the most dangerous attacking outlets in League One this term, with the pair both catching the attention of Championship sides.
Marriott has bagged 17 goals already this term, while Maddison has claimed 13 assists in the league.
Leeds are now said to be interested in the pair, but doing business with Posh could prove problematic.
Peterborough have already turned down offers of £2 million for each of the pair, the Peterborough Telegraph report, and they could cost up to £10 million according to chief executive Barry Fry.
“Interest in Maddison and Marriott is inevitable,” Fry admitted. “We’re prepared for it, but we don’t have to sell them. Obviously if we get bids of £10 million for them it’s a different story, but we have had nothing like that so far.
“We’ve had £2 million bids from Championship clubs, but that isn’t enough for us to even start talking. We don’t want to lose either of them. Maddison has nine goals and 23 assists this season which pretty much makes him irreplaceable.”
Posh chairman Darragh MacAnthony was also asked about the rumours on social media website Twitter, and his response was coy.
No idea Ryan but I guess lot of big clubs would be naive not to look their way etc. That’s nature of the beast in football. All the best https://t.co/dIwUMJ4RHQ— Darragh MacAnthony (@DMAC102) December 28, 2017
Leeds are thought to have money to spend in January, with a forward player one of Thomas Christiansen’s priorities.
Leeds are looking to strengthen their squad, as they aim to return to the Premier League for the first time since 2004.