Ruth Kelly has defended her decision to send one of her children to a private school, saying it was taken on "professional advice".
The communities secretary has come under fire after the revelation that she had moved her son from a state school to a £15,000-a-year boarding school, with one backbench Labour MP describing it as a "slap in the face" for teachers in the state system.
But in a statement released this afternoon, Ms Kelly - who was education secretary until last May - said she had been advised that one of her children had "particular and substantial learning difficulties" and needed specific, specialist support.
"Like any parent, my first thought was to do the right thing for my child. Acting on professional advice - which the local authority accepts - I am placing my son in a school that will be able to meet his particular needs," she said.
Ms Kelly said it was "not uncommon" for pupils with substantial learning difficulties to spend some time outside the state sector. Sometimes this was paid for by the local authority, she said, but in her case she would cover the full costs.
She expects him to be at this school for two years before returning to a state secondary school, while all her other children will continue to be educated in the state system.
"I appreciate that some will disagree with my decision. I understand why, but we all face difficult choices as parents and I, like any mother, want to do the right thing for my son - that has been my sole motivation," Ms Kelly.
Earlier, Downing Street said Tony Blair gave her his full backing, and education secretary Alan Johnson also stressed that parents must be free to make their own choices.
But speaking last night, Labour backbencher Ian Gibson MP said her decision was a "slap in the face for the teachers and pupils in the school that the child has been taken out of", adding: "I deprecate any minister who chooses to do this."
Fellow MP Lynne Jones said she was "saddened" by Ms Kelly's action, which "goes against the principles of the Labour party".
Conservative leader David Cameron said the question of whether a parent should send their child to a private or state school was a "personal matter", and Liberal Democrat education spokeswoman Sarah Teather agreed.
But she added: "Ministers would do well to learn from their colleague's experience. We need a state system that caters for all pupils' needs, however special."
The government currently operates a policy of inclusion, which states that pupils with special educational needs should where possible be educated within mainstream schools. Critics argue that this fails to provide the kind of care many pupils require.
However, Mr Johnson told BBC News 24: "Parents have decisions to make which are very complex about their particular child's future."
He argued: "We want parents to be free to make their own choice, of course, but to find that there's a level of excellence in the state sector that means that really that's where they should send their child rather than the private sector."