Manchester United and Manchester City between them spent £295million this summer on new recruits, amounting to almost three-tenths of all spending by Premier League clubs.
The percentage was inflated by Chelsea's inability to bring in any new faces due to their transfer ban and Liverpool's decision not to bolster its squad with any significant new recruits.
The data - showing that the clubs were responsible for a little over 28% of all summer spending - was collated by Deloitte’s Sports Business Group.
Gross spending by the fierce Manchester rivals was near equal: Manchester City spent most of their £145m on Atletico Madrid's Rodri and Juventus' Joao Cancelo, alongside activating Angeliño's £5.3m buyback clause and signing young American goalkeeper Zack Steffen for around £7million.
A litany of youth players also joined the Citizens, most for nominal fees.
Manchester United, meanwhile, spent slightly less - £140m - on a much smaller pool of players.
Crystal Palace full-back Aaron Wan-Bissaka and Swansea winger Daniel James were recruited, in addition to the club making Leicester's Harry Maguire the most expensive defender in history.
Gross spending in the Premier League was led by Arsenal (£155m), while Aston Villa (£125m) and Everton (£110m) also spent heavily.
These five sides between them spent half of the £1.41billion committed by Premier League clubs, which fell just short of the record £1.43billion from two years ago.
Average spending by Premier League clubs was approximately £71million - up £10million per club from last summer.
"Premier League clubs’ transfer spend continues to be driven by the desire for success on the pitch, ranging from competing at the top of the Premier League and qualification for the UEFA Champions League to simply survival in the top division," commented Dan Jones, partner in the Sports Business Group at Deloitte.
"This summer has seen over half of the Premier League clubs break their individual player transfer records in pursuit of these objectives.”
