The 3969 square metre supermarket at Majura Park will employ 100 staff, have 24 checkouts, 400 trolleys and energy-efficient freezer lights that flicker on when customers approach. Big W will employ 120 people.

ACT Chamber of Commerce and Industry chief executive Chris Peters said there were concerns that Woolworths and Coles already had significant share of the retail market.

''On the other hand, it is a very interesting study that Woolworths has chosen Canberra to take on Costco head to head,'' Dr Peters said. ''It's the first place in Australia that will have those two supermarkets side by side.

''It's a win for consumers and a potential threat for independent retail supermarkets.''

Woolworths regional manager Gavin Murphy said, ''Majura Park is Canberra's newest shopping destination and with anchor tenants like Costco, Big W and Masters Home Improvement, the location represents a great opportunity for Woolworths to bring choice and competition to shoppers.

''We are confident that the growing number of shoppers who regularly visit Majura Park will embrace the supermarket the same way they have welcomed other retailers in the area.''

Much smaller IGA supermarket operators called on the ACT Auditor-General earlier this week to investigate the dominance of Woolworths and Coles despite a competition policy. The Woolworths supermarket at the airport is on Commonwealth land.

Yesterday, Kaleen IGA Supermarket owner Chris Haridemos said Woolworths would turn Majura Park into a ''town centre'' which would be detrimental to other retail sites in Canberra. ''It's very scary,'' he said.

University of NSW Associate Professor of Business Law Frank Zumbo said there were ''potential dangers'' in Woolworths increasing its market size in Canberra because it might lead to a reduction in competition and could push out independent operators over time.

''Where you have independents in the market, prices in these markets are lower than markets where you don't have independents,'' he said. The other risk was ''big box'' developments suffocating existing shopping areas. ''When a Coles or Woolworths sets up a big box outside the town centre, it does have the adverse effect of taking people away from the town centre and over time that town centre gets run down,'' Associate Professor Zumbo said.

Costco, which requires its customers to pay an annual membership fee, said it welcomed Woolworths because it would attract more shoppers to Majura Park.

Asked if the establishment of a retail hub at the airport would hurt retailers in other areas, Costco said it was a wholesale membership warehouse club and its goal was ''to help small-to-medium-sized businesses reduce costs in purchasing for resale and for everyday business use''.

''We hope that we will be able to support the growth of small- and medium-sized retailers throughout ACT,'' a spokesman said.