An unspecified number of buildings at Browndown will be sold, but ministers have vowed that training will continue on the site.
The MoD was unable to say whether they would be sold off to housing developers, which has been feared.
The move is part of a cash-saving exercise aimed at slashing MoD costs.
MP for Gosport, Sir Peter Viggers, said that the buildings on the site were vital to the training facilities.
'The accommodation, the classroom facilities and the open training area near the sea all make it ideally suitable for cadet training,' he said.
'Cadets are a very important part of the recruiting process to the armed forces.
'About a quarter of all cadets go on to join the armed forces and similarly about a quarter of those in the armed forces have graduated through the cadet system.
'This is just undermining the whole point of the site.'
Deputy leader of Gosport council Graham Burgess added: 'I'm concerned that they are going to sell off the buildings and I'm suspicious of their motives.
'There aren't that many buildings on the site and I suspect they will try and use them for development.
'They are looking at every penny in the budget and trying to save any money where they can to make a quick penny to balance the books.'
MoD spokeswoman Rosalind Britton-Elliott insisted cadet training at Browndown would continue.
'However, as a result of a review to increase efficiency and deliver savings to the tax payer, we have identified a number of rationalisation measures, which include the sale of a number of properties on the Browndown site,' she added.
Councillors in Gosport have previously voiced their opposition to any housing development on the site.
Tory council leader Mark Hook said there is no need for more housing in the area and that the MoD needs to have a 'moral responsibility to recognise the damage they do by walking out of sites'.
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