Jim Killock, of the Open Rights campaign group, said: "On the face of it, Nadine Dorries is admitting to breaching basic data protection laws, making sure her constituents' emails and correspondence is kept confidential and secure. She should not be sharing her log-in with interns.
"More worryingly, it appears this practice of MPs sharing their log-ins may be rather widespread. If so, we need to know."
He urged MPs' staff and former staff to get in touch with his campaign "if they have knowledge about insecure data practices in MPs' offices".