The Passport Office is urging holidaymakers to apply for their passports in time as they receive hundreds of calls from parents, holidaymakers and business travellers.
Last December there were 175,174 applications, but this July there are expected to be more than 560,000.
Extra staff are employed by Her Majesty’s Passport Office during summer months but there are limited numbers of appointments at passport offices for fast track and premium services.
Paul Pugh, chief executive of Her Majesty’s Passport Office, said: "The summer months see demand for passports increase up to threefold compared to the winter.
"Check it is valid in advance of your trip and don’t book that trip without first ensuring it is in date."
Statistically, those aged 16 to 20 are the most likely to leave it until the last minute for an adult passport, with about 70,000 applying last July alone.
The Passport Office predicts it will receive around 310,894 Post Office check and send applications, 103,446 Postal Direct applications, 78,478 electronic applications, 40,427 Premium (1 day) counter applications and 27,064 Fast Track Counter (1 week) applications during July alone.
