Tesco has revealed some of its Everyday Value Spaghetti Bolognese contained more than 60% horse meat as MPs demand testing of all processed beef products in the UK.

The grocer withdrew the products from sale a week ago as a precaution because Findus products, which are also at the centre of the row over horse meat, were produced at the same factory.

However, Tesco group technical director Tim Smith said since then tests have identified the presence of horse DNA and although most of the positive results show a trace of less than 1%, three showed “significant levels”, exceeding 60%.

However, Smith insists that no traces off the potentially harmful bute horse drug was found.

He said: “We are very sorry that we have let customers down. We set ourselves high standards for the food we sell and we have had two cases in recent weeks where we have not met those standards.

“The frozen Everyday Value Spaghetti Bolognese should contain only Irish beef from our approved suppliers. The source of the horse meat is still under investigation by the relevant authorities. The level of contamination suggests that Comigel was not following the appropriate production process for our Tesco product and we will not take food from their facility again.”

Meanwhile, environment secretary Owen Paterson has told MPs of plans to test all processed beef in the UK.

Paterson called in representatives of the UK’s producers, retailers and distributors, including the British Retail Consortium (BRC), and said he expected immediate testing across the supply chain. He said testing should take place every three months with the Food Standards Agency notified of the results.

Tesco said it has already begun its DNA testing programme.

BRC director-general Helen Dickinson said: “As we confirmed to the Secretary of State on Saturday, our members take their responsibilities to customers very seriously.

“They are leading from the front on product testing to a tight timetable and being transparent with customers, the Food Standards Agency (FSA) and Government.”

FSA boss Catherine Brown has called for other products including chicken, pork and other meat to be tested for contamination once the beef checks are concluded.