* Chains plan 5 pct expansion vs historic mkt growth of 3 pct
* Competition in non-food retail to get tougher in recovery
* Falling food price inflation to add to pressure on grocers
By Mark Potter
LONDON, May 15 (Reuters) - A big rise in new selling space, a possible steep fall in food price inflation and signs of recovery at rivals in the non-food sector are likely to test the resilience of Britain's top grocers in the coming months.
Supermarkets have been among the best performing business sectors in the recession, helped by their focus on selling essential items and by shoppers trading down to them from restaurants and often more expensive specialist retailers.
Shares in Britain's three big listed grocers -- Tesco, J Sainsbury and Morrison -- have outperformed the benchmark FTSE-100 index by between 17 percent and 27 percent over the past year.
This resilience has even continued this year, when equity markets have been recovering and so-called defensive stocks -- like food retailers -- have been losing ground. Only Morrison has slipped a little off the pace of the broader stock market.
The consistently strong performance has encouraged several big supermarket groups to step up their expansion plans.
Morrison, Britain's fourth-biggest grocer, said in March it had identified over 100 sites for expansion and it would add about 350,000 square feet of selling space, or 10 stores, in 2009-10 on top of a deal to buy 38 stores from rival The Co-Op. It then plans to add 500,000 square feet of space in 2010-11.
Sainsbury, the number three grocer, said earlier this week it planned to step up its expansion rate in 2009-10 to about 5 percent, or 850,000 square feet, from 4 percent in 2008-9, and to keep it at least at that level in the years ahead.
Number two Asda, which is owned by U.S. group Wal-Mart, said on Thursday it was pressing ahead with its plans to open 580,000 square feet of selling space this year and it would like to do more if planning regulations allowed.
Industry leader Tesco is also keeping its foot on the pedal, with plans to add 2 million square feet in 2009-10.
Some analysts think all of this is too much -- equating to about a 5 percent increase in new selling space a year for an industry which historically grows only about 3 percent.
"5 into 3 doesn't go," said Bank of America-Merrill Lynch analyst John Kershaw in a research note this week, noting that each grocer has to expand to keep up with its rivals.
"This can be a real turn-off for investors, given it suggests a highly competitive, highly capital intensive, low growth sector."
INFLATION CHALLENGE
Admittedly, much of the new selling space -- half in the case of Sainsbury -- is being set aside for expansion into non-food ranges, like clothing, homewares and electrical goods.
But Kershaw estimates the increase in grocery selling space will still be ahead of market growth, at about 3.5 percent.
Expansion into non-food may also start getting tougher if tentative signs of economic recovery start to gather pace.
Many of the specialist retailers which have borne the brunt of the downturn in consumer spending will emerge stronger, having cut costs, improved productivity and increased market share amid the demise of weaker rivals.
The challenge for Britain's grocers will be compounded if food price inflation starts to fall, as it has elsewhere.
Rising food prices boost sales and cash flows for grocers, while falling prices can step up the pressure on those that are losing market share to take action, intensifying competition.
"When inflation goes, the picture could turn ugly," JP Morgan analysts wrote in a recent research note.
They pointed to France which has seen a sharp slowdown in food price inflation and where first-quarter hypermarket food sales dropped a like-for-like 2.4 percent at market leader Carrefour and 7.4 percent at rival Casino.
While falling commodity prices have cut food price inflation elsewhere, British grocers have so far been shielded by the recent drop in the pound, which makes imports more expensive.
But unless sterling slides again, this effect will evaporate as it annualises, and could reverse if the currency recovers.
"When inflation comes out of the UK market it will probably be uglier than the euro zone today for the simple reason that the starting point is so elevated," the JP Morgan analysts said.
Nomura analyst Matthew Truman said this week there were signs food price inflation in Britain is starting to fall.
A proprietary survey showed average year-on-year inflation at Britain's top four grocers slowing to 6.1 percent in April from a peak of 9.4 percent, and the first month-on-month fall in average basket price, excluding fuel, for two years.
"We are getting closer to the period of deflation we forecast in 2010, which in turn will put increasing pressure on sales and earnings as a sector," Truman said.
If inflation does fall sharply, there is little agreement over which supermarket group will cope the best.
Nomura believes Tesco will benefit from its scale and that Morrison, which it says is currently showing the highest level of inflation, will suffer the most.
JP Morgan, however, tips Sainsbury to thrive as its reputation for higher quality could be an advantage if shoppers start to "trade up" in an economic recovery. (Editing by David Cowell)