Ocado has dismissed fears that Waitrose could stop supplying it by saying the John Lewis supermarket chain needed Ocado as much as Ocado needed Waitrose.
Waitrose helped the online grocer launch in 2001 with a cash injection and has supplied products since Ocado started trading. Waitrose now competes with Ocado online in the south-east of England and the companies' 10-year supply contract has a break clause in 2017, raising concerns that Waitrose could walk away.
Duncan Tatton-Brown, Ocado's finance director, said: "The arrangement, we believe, brings benefits to both parties. We are the biggest customer of Waitrose and we buy more of their products than anybody else. It means their business is bigger and they can negotiate better terms on products they buy for themselves and they earn money on the products we sell.
"We are not worried at all. We know there are different potential outcomes if either party decided to terminate."
He said Ocado's own products made up a quarter of sales compared with just over 30% from Waitrose, and that selling more own-brand items was an alternative to Waitrose.
Tatton-Brown declined to say whether Waitrose's falling first-half profits in the toughest grocery market for a decade made Ocado's business more important. "Both parties will have contingency plans in case it doesn't continue. We think it will and we hope they will say that they think it will."
On Thursday Ocado announced sales growth at the top end of expectations despite grim trading conditions for food retailers.
Retail sales for the 12 weeks to 10 August increased 15.5% to £218.5m as the average number of orders per week rose 17.4% to 163,000. However, customers spent less per order – £111.64 compared with £113.54 a year earlier.
Tatton-Brown said the smaller purchases were partly because of price pressure but also because customers were ordering more frequently, increasing total sales but reducing the average spend.
The company's shares rose 3.4% to 322.5p – one of the biggest gainers in the FTSE 250 index.
Ocado posted its first pre-tax profit in the first half of this year after 14 years of losses, but doubts remain whether its top-notch systems and strong customer service can withstand competition in the cut-throat grocery market.
Ocado struck a deal with Morrisons last year to run the supermarket's belated entry to online sales. Total group sales, which include those for Morrisons, increased 22.5% to £231.9m.
Morrisons' first-half profits more than halved after it slashed prices and underlying sales continued to drop.
Tatton-Brown said Ocado was not concerned about its partner's woes.
"We are not helping Morrisons with their overall business – we are helping them with their online business. Are we affected by the fact their supermarket sales are down? Not directly."
He said there were no imminent announcements of further Morrisons-style partnerships but that Ocado was talking to lots of companies behind the scenes about running their online operations.
Analysts at Numis, who recommend buying Ocado shares, said: "Despite the tough UK trading backdrop, we remain positive on the shares, encouraged by the solid top-line progress and clear share gains, and seeing huge long-term potential for Ocado to benefit from the shift online and leverage its market-leading IP [technology]."
