The problem was caused by a huge power failure to lastminute.com’s IT supplier, Colt, which also powers a number of other brands in the stable.
Lastminute.com is understood to have failed at approximately 3pm on Friday 4 July, with the other sites following shortly after.
Engineers managed to install a customer service notice to the homepages of lastminute.com and Travelocity.co.uk but visitors to MedHotels and Holiday Autos were greeted with web page error messages.
The Tesco.com travel white label, which is supplied by lastminute.com and has full hotel, flight and holiday search and booking functionality, was also affected by the outage at Colt.
A lastminute.com spokesperson confirmed that the problem was fixed by 2am on Saturday 5 July.
She added: “We would like to apologise to our customers for any inconvenience caused. We’re working with our provider Colt to ensure this doesn’t happen again.”
The problem came during one of the lastminute.com’s peak booking periods, with school holidays just weeks away and consumers looking for late bargains.