J Sainsbury, Britain's third largest supermarket, is poised to splash out £10 million on a rebranding exercise designed to win back lost customers and increase sales by £2.5 billion within the next three years.

The rebranding, which Sainsbury's claims is the most significant in its 136-year history, will be kickstarted tonight with a TV advertising campaign fronted by celebrity chef and good food campaigner Jamie Oliver.

After research showed that customers want help with "simple but effective" recipe ideas, Sainsbury's is launching a new slogan entitled: "Try Something New Today".

The new hook line will feature in supermarkets, on till receipts and on Sainsbury's delivery lorries, and will result in rebranding costs of £2.5 million to the retailer.

This comes on top of the £7.5 million it normally spends on advertising each year and takes the total cost of the exercise to £10 million.

The first advert features an actor dressed as a gorilla in Sainsbury's fruit and veg department, with customers failing to notice him as he picks up goods.

In parallel to the campaign, which begins at 10.45pm tonight, Sainsbury's will be running a two-day training course for 1,000 of its store managers and will give all of its staff lessons in how to give improved customer service by the end of next month.

The move is central to the three-year turnaround programme launched last October by chief executive Justin King and dubbed "Making Sainsbury's Great Again".

Mr King, who retains the support of the Sainsbury family, still the group's dominant shareholders, said: "The announcement marks a change in how we will serve our customers and the start of a company-wide training programme equipping every colleague to improve the customer experience in store."

Mr King will also go on the two-day course.

He added: "Changing how we run our business will mean we can continue to improve our service to customers and sustain the early improvements we have already made.

"Although we have made a lot of progress, significant cultural change is required, particularly at our Holborn [head] office, to deliver our recovery plan and ensure that our stores are at the heart of everything we do because that is where we serve our customers."

The new line replaces "Making Life Taste Better", which has been the supermarkets campaign slogan since 1999.

After two successive quarters of growth in like-for-like sales, the move comes as Mr King's sales-led recovery programme shows signs of taking hold.

In June, Sainsbury's said that in its first quarter - for the 12 weeks to June 18 - like-for-like sales excluding petrol rose by 1.3 per cent. Including petrol sales, they rose by 1.9 per cent. Total group sales for the first quarter were up by 5.7 per cent.

In March, Sainsbury's reported that underlying sales had grown for the first time since July last year and that it was beginning to poach back customers from William Morrison and Asda, both of which have been feeling the heat of the downturn in consumer sentiment.

His price-cutting approach led Mr King to slash the cost of 6,000 items last year; he claims since the beginning of this year to have cut prices on a further 1,000 items. A further 3,000 workers have also been hired to help ensure that supermarket shelves remain fully stocked.

Since its health first began to deteriorate Sainsbury's has been the subject of peristent takeover rumours, the latest of which involved Carrefour of France.

The group has been linked with Allan Leighton, the chairman of the Royal Mail, and Archie Norman, the former MP. It has also been reported that private equity groups have regularly run the slide rule over Sainsbury's and have explored possible bids.

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