Well, neither actually.
Freeview HD will be broadcast in 1080i (interlaced). This is the same format as used in Sky HD and Freesat HD.
What does this mean? Well the number, 1080, represents the number of rows of pixels from top to bottom. So a 1080p LCD TV has 1080 rows of pixels. The letter next to 1080 (i.e. 1080i or 1080p) stands for either ‘interlaced’ or ‘polarised’. In theory, 1080p is better than 1080i. 1080p is referred to as Full HD.
So if a Full HD LCD TV is 1080p, what about TVs that are 720p or 720i? These are known as HD Ready and these usually have a vertical resolution of 720 – however, 1080i TVs are also called HD Ready.
So, a 1080p Full HD TV or a 1080i HD Ready TV will display Freeview HD in its full glory. An 720i or 720p HD Ready TV will also display Freeview HD, but it will have to digitally process the picture to shrink the 1080 horizontal rows to fit its 720 screen.