The numerous cost overruns and delays that have plagued the federal shipbuilding strategy are being blamed on overly optimistic planning for the multibillion-dollar project.

Karen Hogan's warning was contained in a new report that offers a scathing assessment of Ottawa's multibillion-dollar national shipbuilding strategy.

The move follows a complaint last week from an Ontario shipyard to the Canadian International Trade Tribunal that the government was unfairly stacking the deck in favour of Quebec's Chantier Davie yard.