The defendant, Nigel Evans, faces nine charges of indecent assault, sexual assault and rape.
Prosecutors say he used his position to make or break careers and to sexually assault seven young men.
The 56-year-old resigned as deputy speaker after his arrest last year but has remained in Parliament. He is a senior member of the Conservative Party.
Prosecutors today listed Bercow and six other lawmakers as witnesses in the case.
Evans denies all the charges against him. The seven alleged victims are all adult males who cannot be identified for legal reasons. Some of the alleged offenses date back to 2002.