Express Newspapers is claiming to have put on 500,000 extra sales over the course of four days after paying TV presenter John Leslie for his story.
The group has also indicated that it may sue rival news organisations for breach of copyright after accusing them of lifting chunks of the Leslie interview.
Express Newspapers paid Leslie and his family around £550,000 for the exclusive rights to interviews and pictures.
Last Thursday, the former This Morning presenter had two charges of indecent assault against him dropped.
Since then the Daily and Sunday Express have contained extensive coverage of the Leslie story.
Daily Express deputy editor Nicola Briggs said of the Leslie story: “It’s been a fantastic success. It was a story that everyone wanted and we’ve left the rest of Fleet Street trailing.” She added: “The blanket copying by The Sun and the Mirror of substantial parts of our interview is outrageous and we’ve reported the matter to our lawyers.”
A spokesman for Express Newspapers said solicitors’ letters have now been sent to the papers concerned.