Business travel sales through leading corporate agents dropped by almost 5% in August over the same month last year.
The Guild of Travel Management Companies attributed the 4.7% decline, revealed in latest BSP figures, to the London 2012 Olympics effect.
Air sales through all BSP agents fell by 3.24% in the month.
Year-on-year sales by all BSP agents decreased 1.88%, with GTMC members down by 0.88%.
Average transaction value for GTMC members showed a decline of 2.39% in August but slightly up year on year by 1.12%.
The average transaction value for all BSP agents was down 3.56% in the month and also dropped by 1.49% year on year.
GTMC chairman Ajaya Sodha (Key Travel) said: “The drop in air sales by GTMC members was probably due to the Olympics’ effect combined with the traditional holiday season.
“August is always traditionally slow and now UK PLC is back at work full on we await the September figures to get a truer picture.”