The Post Office has urged people to check their passport details ahead of the start of the summer holiday season.
The warning is to make sure they people travel without any problems.
Official Government guidance is that it takes three weeks for a standard passport renewal, but the Post Office said this could take longer if applying for the first time.
The Post Office said its research suggested that more than a third of UK people are unaware of their passport expiry date without having to check and one in four have forgotten to renew their passports before it expired at least once.
The Post Office said it wanted to raise awareness to avoid any potential complications for holidaymakers as they travel to other countries this summer.
Elinor Hull, identity services director at the Post Office, said: “Customers are advised by His Majesty’s Passport Office not to book travel until they have a valid passport.
“As our research shows that many customers do not do this, and with the summer holidays fast approaching, it’s crucial for travellers to ensure their passports are up-to-date to avoid any unexpected surprises at the check-in desk.
“Six weeks before the peak summer travel period, we want to remind people across the country to take a proactive approach in safeguarding their travel plans, to ensure holidaymakers have peace of mind, and a renewed passport, in time for their holidays.”
Meanwhile, Martin Lewis warned holidaymakers to check two documents before they travel because of a rule change.
Speaking on The Martin Lewis Money Show Live summer special on Tuesday, 11 June, the MoneySavingExpert founder told viewers they need to review their GHIC card and their passport.
The GHIC lets travellers get necessary state healthcare in the European Economic Area (EEA), and some other countries, on the same basis as a resident of that country.
Lewis urged viewers to check their card’s expiry date before travelling, as well as that their passport is under 10 years old.
Some countries need at least six months, or even three months, left on it to be let in, he added.