The boss of Australia's biggest car dealership group says the performance of the Automotive Holdings Group business acquired two months ago in a $2 billion merger has been ''disappointing'', although it's not unexpected in a weak new vehicle market.

AP Eagers chief executive Martin Ward said the soft industry conditions meant the broader AP Eagers operations were having a difficult time, with underlying operating profit before tax down 6 per cent for the 10 months ended October 31. AP Eagers shares dropped by 6.9 per cent to $11.03 by 2.30pm (AEST). They have tumbled 22 per cent since October 7 when the stock was at $14.15.