Duncan has been tasked with growing sales and subscriptions of newspaper titles in print and digital, as well as seeking out new revenue opportunities.
Meanwhile David Robinson, previously the director of betting and gaming, has been appointed managing director of The Sun and The Sun on Sunday.
The publisher of The Sun and The Times merged the ad sales teams of the two titles in 2008 as part of a strategy to sell them together, but reversed this in March after The Sun’s website dropped its paywall.
Commercial sales across the titles remain the responsibility of Dominic Carter, News UK’s chief commercial officer. Carter’s move to split the sales teams contrasts with publishers such as Telegraph Media Group and Mail Brands.
Jeff Misenti, who joined News UK from sister News Corp company Fox News earlier this year, will take up the newly created role of managing director of audience, insight and experience. His team will be charged with "being at the cutting edge of tech", as well as understanding News UK’s data and delivering audiences to advertisers.
David Dinsmore, News UK’s chief operating officer, said: "The business models for our titles have evolved and are now clearly defined. The Times and The Sunday Times reach a valuable, premium audience, and The Sun and The Sun on Sunday reach a popular audience at significant scale on a daily basis.
"It has become increasingly necessary to have separate leadership and to change the structure of my senior team and I am confident that these changes will enable us to focus on driving sustainable revenue streams for our titles in their respective markets."