NEW DELHI: Calling for a rethink of its submarine building programme, Defence Minister Manohar Parrikar today said India should look for greater numbers than the existing plan of constructing 24 such vessels.Referring to the existing 30-year submarine building plan that envisages construction of 24 submarines, including both nuclear and conventional, Parrikar said India needed a longer term plan till 2050. The existing plan ends in 2030.He also said that the strategic partnership model is in the last stage and once brought out, the ministry will fast- track the P75 India project under which six more conventional submarines are to be built.He rued that unlike the ongoing nuclear submarine project, the indigenisation on the Scorpene projects is very low (30-40 per cent).Parrikar emphasised on the need to retain skill and skilled people engaged in submarine contruction and said the focus should also be on maintainance."We need to rethink about the real requirement based on our projection... We also need to assure that the skilled manpower and skills developed need to be retained," he said.The minister noted that prime contractors are chosen through stringent criteria aqnd are nurtured through award of contracts on sustained basis so as to retain the industrial base skills, capabilities and technology.He said that Russia has built 595 submarines till date while the US has constructed 285 submarines.On startegic partnership, he said, "It has already been approved and the drafting of the chapters is underway. Approval is needed by the Defence Acquisition Council (DAC) and probably by the Cabinet as well as it has financial implications," he said.Parrikar also called for a higher level of indigenisation in submarine-building. "Indigenisation in Scorpenes is not up to the mark, but in the Advanced Technology Vessel (ATV) programme (nuclear submarines) it is over 70 percent," he said.