The government has put passport services under strain with fewer staff but greater responsibility since 2010, Ed Miliband said at Prime Minister's Questions.
The Labour leader told MPs the problems showed the Home Secretary had "not been paying attention to the business of government" during her row with Education Secretary Michael Gove.
The Home Office has outlined how people who are facing delays to their passport renewal can get it fast-tracked for free.
If you are worried about your passport application not being ready ahead of your holidays, there are a few options available to you.
Photos shown to ITV News appear to reveal the scale of the backlog at the Passport Office, amid staff claims of "blind panic".