Britain's second largest supermarket chain last night launched an investigation into allegations that workers who make its clothes in Bangladesh are being forced to work up to 80 hours a week for as little as 4p an hour...a spokesman for Asda said that it would re-audit all its Bangladeshi factories in the light of the Guardian's findings...Primark said that Labour conditions were a matter of "considerable concern"...A spokesman for Tesco said it could not take any action because it was not provided with the names of the factories concerned...He added that Tesco had recently completed unannounced audits at all 48 sites in Bangladesh. [also refers to Luman Group]