Burger King has tonight admitted that it has been selling burgers and Whoppers containing horsemeat despite two weeks of denials.The fast food chain, which has more than 500 UK outlets, had earlier given a series of â€˜absolute assurancesâ€™ that its products were not involved.However, new tests have revealed these guarantees were incorrect in a revelation that threatens to destroy the trust of customers. It also raises serious questions about whether the food company, which sells around one million burgers a week in the UK, has any good idea about what goes into its products.The contaminated burgers were made by the Irish-based processing company, Silvercrest, which is part the ABP Foods Group. The same company also made tainted burgers for Tesco, Asda and the Co-op, among others.Burger King has faced allegations of orchestrating a cover-up of its links to the horsemeat scandal in order to give it time to find an alternative supplier.It is currently shipping in tens of thousands of burgers from suppliers in Germany and Italy in order to meet demand at its UK outlets.It is known that the management at Silvercrest has been using a series of non-approved ingredients in their burgers for a range of household name brands.These included meat off-cuts, including horse, that were imported in large frozen blocks from Poland.The contamination has been going on since at least last May and potentially for up to one year, according to evidence presented to MPs earlier this week.Tonight Burger King abandoned its earlier denials, saying: â€˜Four samples recently taken from the Silvercrest plant have shown the presence of very small trace levels of equine DNA. Within the last 36 hours, we have established that Silvercrest used a small percentage of beef imported from a non-approved supplier in Poland.â€˜They promised to deliver 100per cent British & Irish beef patties and have not done so. This is a clear violation of our specifications, and we have terminated our relationship with them. â€˜Through our investigation, we have confirmed that this non-approved Polish supplier is the same company identified by the Irish Department of Agriculture as the source of Silvercrestâ€™s contamination issue.â€™[h=2]'We are deeply troubled by the findings of our investigation and apologise to our guests, who trust us to source only the highest quality 100per cent beef burgers.'[/h] - Burger King vice president The contamination scandal was first triggered two weeks ago, with the Food Safety Authority of Ireland revealed it had found horse meat in burgers sold in Ireland and the UK.When the news first emerged, Burger King said it had been given an â€˜absolute assuranceâ€™ by its supplier that its products were not involved.Yesterday, Burger King vice president, Diego Beamonte, said: â€˜We are deeply troubled by the findings of our investigation and apologise to our guests, who trust us to source only the highest quality 100per cent beef burgers.â€˜Our supplier has failed us and in turn we have failed you. We are committed to ensuring that this does not happen again.â€™ He added: â€˜We will dedicate ourselves to determining what lessons can be learned and what additional measures, including DNA testing and enhanced traceability controls, can be taken to ensure that we continue to provide you with the quality products you expect from us.â€™Jeanette Longfield, of the campaigning food and health group, Sustain, has condemned Burger Kingâ€™s handling of the problem.