General Sir Mike Jackson retired in 2006
A former head of the Army has called for a "real public debate" over the amount of money spent on defence.
General Sir Mike Jackson said military spending had not been reviewed for 10 years and should be put to the top of the political agenda.
He also said improvements to soldiers' housing could be easily achieved, but would require strong leadership.
The government said the defence budget was in its longest period of sustained real growth for 20 years.
Sir Mike said in an interview with The Monitor magazine: "What needs to happen is a real debate on what proportion of the national wealth we should be spending on defence.
"We should urgently be asking: what capabilities do we really need to be sure that we're well insured in the future?"
He said defence has not "been on the radar screen" for the past two elections and it would be healthy to have a debate on its long-term future.
And Sir Mike also said it was "outrageous that some soldiers are living in grotty accommodation and that could be solved quite easily."
"That money can either come from raised taxes, which creates shock and horror; it could come off another government spending department like health or education, causing equal shock and horror; or it must come from elsewhere in the existing defence budget.
"Those are the three stark choices. That nettle has never really been properly grasped and I would like to see it grasped."
A Ministry of Defence spokesman said the Treasury provided "significant amounts" of new money to pay for operations on top of the core defence budget.
He said the government acknowledged there were serious problems with accommodation, because of decades of under-funding.
"We are making real progress to put this right and we are investing more than £8 billion in military accommodation over the next 10 years," he said.
Shadow defence secretary Liam Fox said the Conservatives had been "repeatedly calling" for a defence review.
He said: "We are pleased that Sir Michael has chosen to lend his considerable military experience to put further pressure on the government."