Tesco has taken out full page adverts in the national press as it seeks to reassure motorists that its petrol is now safe following the contaminated fuel crisis.

The source of the problem has been identified as high levels of silicon, which were found in four storage tanks at the Vopak terminal in West Thurrock, Essex. Harvest Energy shares facilities at the depot with Greenergy, which supplies Tesco. Greenergy said that a component understood to have been used by Harvest Energy had tested positive for excess levels of silicon.

Having taken the brunt of the media coverage, Tesco’s adverts state that its fuel is "back to normal and we’re sorry", with all the affected sites in the south east having been "refuelled with a fresh, clean supply". The supermarket chain also promises to pay for damage caused by the rogue batch of fuel, which affected around 150 sites.

A Tesco spokesperson admitted that the situation had been frustrating: "We’ve taken a lot of flack for something that wasn’t our fault," he said."The source has been traced back to Harvest Energy, who aren’t even our supplier. It’s too early to say how badly it’s affected sales."

Asda has also replaced its petrol stocks at around 30 sites. A spokesperson said that the company had received hundreds rather than thousands of complaints from customers and would reimburse those whose vehicles had suffered damage.

Morrisons, meanwhile, has stopped selling unleaded at 41 sites until further tests have been completed. A spokesman said: "If any evidence of contamination is found we will flush through the tanks. We will then take necessary steps to ensure our customers know about the situation, although we can’t say what format this will take at this stage. This is a localised problem and we don’t believe it’s impacting too much on sales in other areas."