The UK's fourth-biggest grocer delivered a worse-than-expected 1.6% decline in underlying sales in the six months to the start of August, while pre-tax profits dived 22% to £344 million.
It said customers' incomes are shrinking under relentless pressure from stubbornly high inflation, as the recovery proves "slow and fragile".
Customers are increasingly shopping about for bargains, it added, with more than 40% visiting multiple supermarkets on one shopping trip, and they are buying less food as they stick rigidly to budgets.
But the chain reported more progress with expanding its network of convenience stores. It is trading from 33 and expects to have 100 by the end of its year.
Chief executive Dalton Philips said like-for-like sales are steadily improving after falling 1.8% in the three months to May 5, adding he expects another sales improvement in the second half as its turnaround bears fruit.
Morrisons said it is on track to start selling food online - through a tie-up with internet grocer Ocado - by the end of January.
The chain said: "Whilst there are early signs that the UK economy has started to turn a corner, the grocery market continues to be a very challenging environment in which to operate.
"Consumers are continuing to react to these pressures by becoming more discerning, and seeking to get better value for money by both shopping across multiple channels and using innovative approaches to the way they shop."
Morrisons also joined rivals in signalling an end to rapid expansion of new space. It will slash its space growth to around half the rate over the past five years, at 350,000 square feet annually.
In future it expects sales growth mainly to be driven by online and convenience, both of which use less capital than opening big new stores.
Turnover was level at £8.9 billion, but net debt surged to £2.5 billion from £1.7 billion a year earlier as it invested heavily.
Analysts had on average been expecting like-for-like sales to decline 1.5% over the half. They expected pre-tax profits to slide 13% to £383 million from £440 million a year earlier.