The group's Edinburgh-based bank meanwhile has said this week's launch by Glasgow-based Tesco Bank of a current account will not prompt an acceleration of its own plans, with Sainsbury's Bank unlikely to enter that market for at least two years.
Sainsbury is hoping not to do a Tesco, where sales growth started faltering soon after long-serving chief Sir Terry Leahy stepped down, hitting a 40-year low in the first quarter of 2014.
After reporting a shock 3.1 per cent sales fall in the final quarter of 2013 after nine years of almost unbroken growth, Sainsbury, which has 82 stores in Scotland, has now added to that a 1.1 per cent decline in the first quarter of 2014.
But Mr King, who will be succeeded by commercial director Mike Coupe on July 9, said he was not handing on an empire in decline. "I would have preferred sales to be growing but I don't think it is leaving on a low - if my tenure was judged on one-quarter that would be sad but (anyway) our relative outperformance if anything is a better one than it has been for a while."
The grocery market is growing at its slowest rate for 11 years and the "big four" are all being outpaced by discounters Aldi and Lidl, and upmarket chains Waitrose and Marks & Spencer.
But Mr King insisted: "I am not going to have a post-Sainsbury epiphany, because I believe strongly in this business and its positioning with customers."
He said the discounters' promise of 80 new stores this year reflected "changing shopper behaviours rather than a fundamental shift to price", adding: "We think longer term, customers will stay solid as they have done through the downturn."
Mr King said stripping out inflation from the sales numbers suggested that volumes in the group's core stores were down around 2 per cent year on year, adding: "There is no doubt there is a price skirmish going on as we speak, we have said very clearly we will stand toe to toe, in the next quarter we have the strongest price position we have had in a very long time."
But both Mr King and Mr Coupe stressed Sainsbury's "values" - the chain believes it can differentiate itself through own-brand products, the provenance of its food, and investment in convenience and online, the two fastest-growing channels.
Mr King said: "Our complementary channels and services are an increasingly important component of our growth, with sales from convenience and online nearly doubling over the last five years to 15 per cent of total sales."
Sainsbury last month forecast underlying sales growth for the year similar to the 0.2 per cent achieved in 2013-14 - well ahead of Tesco and Morrisons, who have both flagged negative like-for-like sales as they cut prices, fuelling analysts' concerns that a price war will damage earnings across the sector.
Asda is the best current performer of the big four, according to monthly data published last week, while Sainsbury's market share has slipped 0.2 points to 16.5 per cent year on year.
Chief financial officer John Rogers said Sainsbury's Bank was busy transitioning onto a new IT platform. He said: "That is going to be the focus of the team in the next 24 months or so."
John Ibbotson of consultancy Retail Vision, said: "Justin King's plans to quit on a high have been scuppered, but in fairness he's done better than most to tackle the sea change within retail."
George Scott, a retail consultant at Conlumino, said the supermarket's refusal to be drawn into an all-out price war with discounters was a sensible strategy over the long term.
He added: "The grocery game is a long one and, as austerity eases, Sainsbury's will benefit as consumers scrutinise wider attributes of their shopping purchases, broadening their consideration of price, quality, provenance and service."
HSBC analyst David McCarthy said while Sainsbury was doing better than some of its rivals the key fact was it was still losing sales.
Sainsbury shares were up 3.2p at 333p.