America's two biggest shock jocks just got a shock of their own. In a major blow to their broadcasting dominance, the second-largest radio station owner in the US is said to be dropping both Rush Limbaugh and Sean Hannity from its airwaves.

According to a report by Politico, Cumulus Media has decided not to renew contracts with the two talk radio titans at the end of 2013, meaning their radio shows will vanish from more than 40 of its stations across the US.

Limbaugh and Hannity remain the highest-rated talk radio hosts in the US, with Limbaugh regularly claiming a listenership of 15 million. In 2012 he suffered a significant blow to his reputation, after describing 30-year-old graduate law student Sandra Fluke as a "slut" and a "prostitute" on his show.

Fluke had campaigned for Georgetown University to offer free contraception to students. An anonymous Cumulus executive recently told trade title Radio Ink that "48 of the top 50 network advertisers have 'exclude[d] Rush and Hannity' orders," which prohibit their ads from appearing during Limbaugh's and Hannity's shows. Following the Fluke furore, bloggers had called for an advertising boycott; at least 100 firms deserted Limbaugh, including AOL, Sears, John Deere and Netflix.

Cumulus chief executive Lew Dickey attributed $2.4m (£1.56m) losses to the "syndicated talk segment" to which Limbaugh and Hannity belong.