Lloyds TSB shareholders were “mugged” when the bank agreed to buy HBOS last year without knowing that the stricken lender was being propped up by a secret £25bn loan, Jim Cousins, a Labour MP, said on Wednesday. Alistair Darling, the chancellor, was forced on to the defensive as he gave a Commons statement explaining the decision to keep secret the combined £61.6bn of emergency funds given to HBOS and RBS last year. Lloyds bought HBOS in a deal facilitated by Gordon Brown, who waived competition rules to allow the merger to take place.