UK grocer Waitrose has continued to book market-beating sales gains in the first half of the year and said it plans to accelerate investment to drive growth.

The supermarket group, the grocery arm of The John Lewis Partnership, said revenue grew 8% to GBP2.85bn (US$4.5bn) in the six months to 27 July.

Like-for-like sales rose 6.9%, excluding petrol, and customer transaction numbers were up 9.3%. During the period Waitrose opened four outlets – two in its core supermarket portfolio and two convenience stores.

Sales at were up 40.9% and the company said it benefited from its omni-channel approach during the period.

Sales gains outpaced the overall UK grocery sector and Waitrose emphasised its market share grew to 4.9%, 0.3% higher than a year ago.

The company said Waitrose invested GBP101.0m in the period, mainly on branch openings and the new Leyland regional distribution centre – which will support the group’s expansion in northern England and Scotland. The retailer also said it is looking to drive “productivity” and “flexibility” through investments in supply chain and retail systems. Investment levels will accelerate in the back half of the year, the group added.

Waitrose also saw an increase in operating profit, which totalled GBP160.2m, up GBP18.2m, or 12.8%, on the comparable period of last year.

However, the Partnership revealed one-time costs dented group profit before tax, which includes the result from the firm’s department store chain John Lewis. Group pre-tax profit was down 38.5% to GBP68.5m. Excluding exceptional items, including higher pension costs and a review of the firm’s holiday pay policy, pre-tax profit rose 3.9%.