However, he said the government had invested huge sums in recruiting more regular troops to the Army on the advice of military chiefs.
As result, it was recognised that funding for other areas of the defence budget would have to be "reprioritised".
While he said TA members would be "disappointed" by the reduced activity, he said he hoped they would recognise the reality of the financial situation and that the Afghan mission must remain the UK's "main effort".
He said he had "listened" to concerns about the future of the TA and was adjusting his proposals for their training to help the "continuity and retention" of units.
The changes mean the TA's budget this year will be cut by £17.5m, rather than the £20m originally proposed.
It was "emphatically" not the case that troops due to be deployed to Afghanistan would see their training cut back, Mr Rammell said.
"No TA soldier will be deployed on operations unless the Army is satisfied he is properly trained and prepared," he said.
Shadow defence secretary Liam Fox said the TA's annual budget was effectively being cut by £43m and argued it was vital that routine as well as pre-deployment training should be protected.
The TA has had an increasing burden put upon it in recent years
Nick Harvey, Lib Dem defence spokesman
"For many the TA is a habit," he said. "Break the habit and you break the TA."
He added: "The proposals are a shambles and they must be reversed."
For the Lib Dems, defence spokesman Nick Harvey said the amount likely to be saved was tiny compared with the long-term damage it could do to morale within the territorials.
"The TA has had an increasing burden put upon it in recent years. If it were not for their efforts and the skills they bring from civilian life we would have struggled with our operation in Afghanistan in recent times."
Mr Hoyle urged the armed forces minister to reconsider his plans.
"I am sorry for you that you are becoming an apologist for a crass decision," he said.
"The problem we face is that quite rightly you say we have got to make tough decisions, hard decisions but that should not be the wrong decision and that is what we have seen."
Eric Joyce, an ex-aide to the defence secretary, said the situation was not "ideal" and the decision must be kept under review to ensure recruitment and retention of territorial soldiers was not damaged.
The future of the TA has risen up the political agenda in recent weeks with more than 500 reservists now serving in Afghanistan.
Conservative leader David Cameron has claimed some reservists are not getting the training they need before being deployed abroad but ministers have denied this.
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