Wesfarmers chief executive Richard Goyder has revealed that two Bunnings hardware outlets recorded an immediate drop in sales when Woolworths opened its maiden Masters big-box hardware store nearby.

The admission that Masters, which opened its first hardware site in August, has peeled customers away from industry heavyweight Bunnings in the short term will embolden arch rival Woolworths as it seeks to roll out as many as 150 stores nationwide.

However, it is still early days in the hardware war being fought between Wesfarmers and Woolworths with Mr Goyder also signalling the conglomerate which also owns the Coles supermarket business would be reinvesting in staff and service at its Bunnings outlets.

Speaking at a press conference after the release of Wesfarmers first-quarter sales results, Mr Goyder said it was too early to gauge the sales impact to Bunnings stores located near four Masters stores recently opened in Queensland but there had been a sales drop for the group following the opening of the Masters hardware site in Braybrook, located in inner-west Melbourne.

"There has been some impact on the two stores next to Braybrook, sort of in line with our expectations - you would expect some impact," Mr Goyder said.

He declined to detail Wesfarmers's initial expectations of the potential drop in sales for a Bunnings located near a new Masters store.