Can it be everything to everyone, or should it focus on its gem, the British grocery business?

A WEEK from today, Tesco chief executive Phil Clarke will deliver what may well turn out to be the most crucial presentation of his career – and a watershed moment for Britain’s biggest retailer.

On April 18th, Tesco reports its full-year results for 2011/2012. The figures will be accompanied by Clarke’s blueprint to revitalise the group’s core, but ailing, UK operations. His plan to restore growth to the group is impatiently awaited in the City, which has become increasingly critical of the business and its management team in recent months.

Clarke, a Tesco “lifer” who started stacking shelves as a schoolboy almost four decades ago, took over the top job from Sir Terry Leahy little more than a year ago.

It’s been a torrid 12 months: in January £5 billion (€6 billion) was slashed from the retailer’s stock market value as the new chief executive presided over an unprecedented profit warning following a shock fall in Christmas sales.

Since then, with market share in its core UK business sliding to a seven-year low, Tesco’s reputation as a profit-making machine has taken a severe battering.

And, unheard of until recently, doubts are being raised over its strategy on several fronts, from the group’s costly foray into the US and its much-delayed plans to set up a banking business in the UK to the lacklustre state of its chain of stores.

Pressure is mounting ahead of next week’s presentation. Over the weekend one of the group’s leading investors broke cover to voice his concerns publicly.

Richard Black of Legal General Investment Management, Tesco’s fourth largest shareholder with a stake of 4 per cent, gave the group some advice via the columns of the Sunday Times: “It needs to think long and hard about what it wants to be,” Black told the paper. “Can it be everything to everyone, or should it focus on its gem, the British grocery business?”

Even more galling for Clarke and the Tesco team were comments from rival retailer Justin King, chief executive of Sainsbury’s. Breaking the unwritten rule that one company boss doesn’t criticise another (not on the record, at least), King effectively accused Tesco of failing its customers, saying service in Sainsbury’s shops was “significantly better” than that at Tesco.

Nor will Clarke have been pleased to discover – again, via the columns of a newspaper – that the Sainsbury’s chief executive has a framed newspaper article from January on his office wall: “UK sales fall is first for Tesco in 20 years,” the headline reads.

According to Black, Tesco needs to pour as much as £1 billion into the ailing UK operation if Clarke is to restore it to growth. Other critics want the plug pulled on the group’s Fresh Easy venture in the US, which they say is not only eating up cash but too much management time.

Clarke has said the business is moving closer to break-even but many fear that the profits, when they come, will be too little and too late. There are similar fears with Tesco’s delayed plans to offer customers a full banking service.

Clarke has already unveiled several measures. Last month he took personal control of the UK stores operation after the departure of its head, Richard Brasher, who carried the can for the failure of the group’s “Big Price Drop” campaign (renamed in the City as the “Big Price Flop”).

He also announced that 20,000 Tesco jobs would be created in the UK over the next two years, with a particular focus on customer service in the stores.

The group’s 20-year-old Tesco Value range, known for its blue-and-white striped packaging and rock-bottom prices, is being junked in favour of a more brightly coloured and higher quality Everyday Value range.

The group has also admitted defeat in its move into the online used-car market, which has now been abandoned after a year.

Clarke’s task next week is to convince the City he has a workable, affordable plan to shake the dated look from Tesco’s sprawling stores chain, as well as a price strategy that will woo back the customers who have defected to rival retailers in recent months.

If he can’t convince investors of that then the Tesco chief is likely to be dealt with harshly in the City, as he was with the profit warning in January.

The last thing Clarke needs next Wednesday is more headlines King might be tempted to add to his office collection.

Fiona Walsh writes for the Guardian newspaper in London