Applicants for British passports who paid additional fees in an attempt to avoid processing delays should get a refund, MPs have argued.

‘Fast-track’ appointments, often promising passports would be returned in 24 hours, “exploited” travellers, according to the Home Affairs Committee.

At one point in early summer, the number of outstanding requests went above half a million.

Problems with passport applications came to public attention in the summer.

At its peak in late June, the number of outstanding applications reached 537,663.

Ministers at the time blamed “exceptional demand” at the Passport Office, but have said the situation has since improved.

To ensure this situation did not disrupt summer holiday travel, the Passport Office took on extra staff, extended opening hours, increased overtime and redeployed workers from elsewhere.

In mid-June it announced that - for people who could prove they were booked to travel within seven days and had submitted passport applications more than three weeks earlier - there would be a free upgrade to its fast-track service.