The pair will join O2 in the latest move to push the limits of how much of the booking process can be carried out through a mobile phone.
All three networks are using Handy Traveller technology created by Handy Phone.
Phone users will be able to search for holidays through a network’s 3G browsing system, before making a booking and sending payment details direct to a site.
The addition of T-Mobile to its portfolio comes following the appointment of Alan Bates as the Handy Group’s new chairman.
According to chief executive Michael Lacy, Bates, a former chief executive of Bell Cablemedia before its sale to Cable & Wireless, is best placed to steer the company into the next stage of its development.
“Alan brings to the board his valuable experience in strategic planning and communications and an excellent commercial overview,” Lacy added.