Potential recruits will take part in 12-week military training exercises run by the Prison Service. The Army will then carry out its own assessment of proposed candidates.
Offenders will only be considered if they have been sentenced to two years or less, and those convicted of sex, drug or race crimes will be disqualified.
Details of the scheme have emerged despite concern among senior officers that it should be kept low-key. The Army is thought to be keen to avoid a repetition of the criticisms that accompanied last year's plans to recruit homeless youngsters living in Leeds. There are also fears that the scheme could anger gay rights protesters who are still trying to overturn the Army's ban on homosexuals.
Critics claim that the scheme is scraping the bottom of the barrel because the Army cannot find enough recruits through traditional methods.
The Conservatives' defence spokesman, Iain Duncan Smith, said: "This is typical of the Government. Our military services are so overstretched and desperate for soldiers that they are entertaining the idea of going into prisons to recruit.
"Who will they recruit and what sort of crimes will they have committed? The proposals leave these questions unanswered and we are deeply concerned about them."
However Ann Widdecombe, the shadow Home Secretary and a former prisons minister, said: "I think most people would agree that a spell in the Army is the best thing for a lot of these people."
Colonel Wayne Barber, who is leading the recruitment drive, said: "We are trying to be more inclusive. We are not lowering standards or scraping the barrel. We are trying to help people who have made a mistake in life and paid for that mistake. We believe military service will offer the chance of returning a better citizen to society."
Convicted criminals were banned from joining the Army until three-and- a-half years ago, when the rules were relaxed. Since April, the Army has received 29 applications from young offenders, 14 of whichhave been approved.
The scheme has been set up amid concerns that the British Army is now too small to meet its commitments. Its official strength is 109,000 but the number of fully trained personnel is just over 90,000.