Britain’s biggest supermarkets face another grilling this week after it emerged today that the Competition Commission will announce the outcome of its two-year investigation into the £120 billion sector on Wednesday.

The Competition Commission is expected to propose strict planning tests to curb Tesco’s dominance in the UK and call for the creation of a new "shopping czar" to settle disputes between the supermarket chains and suppliers.

The move comes only days after the Office of Fair Trading (OFT) started its latest investigation into the alleged price-fixing between the supermarkets and their suppliers.

The OFT visited the head office of Tesco, J Sainsbury, Asda and Wm Morrison last Thursday requesting data about the prices of groceries, health and beauty products and detergents.

Unilever and Procter & Gamble are also part of the investigation.

The co-ordinated visits followed a humiliating climbdown by the OFT last Wednesday, when it was forced to apologise to Morrisons and pay £100,000 in damages to settle a libel action linked to a probe into alleged price-fixing on milk.

Supermarket insiders claim to have little idea as to the reason for the latest raids. One executive described the visits as a "fishing exercise".

In a statement yesterday, Tesco said: "We are confident that we always act in the interest of consumers. Over the last 10 years we have saved the average family almost £5,000 as a result of our investment in price."

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