That's according to official ChartTrack figures obtained by MCV, which show that Xbox 360 took a 55 per cent share of the combined sales of the game.
However, PS3 hardware sales leapt 127 per cent in the week in which the game was released (Sunday, April 27th to Saturday, May 5th).
Xbox 360 hardware sales also felt the GTA effect, climbing 125 per cent in the week.
According to ChartTrack data, the title also broke single-format, first-week sales records on both console.
It sold 514,000 copies on 360, making £22 million in revenues at UK retail. The previous record holder, Halo 3, sold 411,000 copies in its first week, making £16.9 million.
On PS3, GTA IV sold 413,000 copies in the week, taking £17.9 million at retail. That beat the previous one-week record holder, GT5: Prologue, which sold 120,000 and made £2.6 million.