The former paratrooper, who suffered massive injuries in Afghanistan, is suing the Ministry for breach of statutory care, the Mail on Sunday has said.
Lance Bombardier Parkinson is claiming his pay has been cut, vital medical treatment put in jeopardy, and that the Whitehall department has failed to provide him with wheelchairs.
Ben, 33, lost both legs and suffered brain damage when his Land Rover hit an anti-tank mine in Helmand Province in 2006.
"Mr Parkinson's position is that the MoD breached its statutory responsibility to provide him with the care he requires," said Yogi Amin, from lawyers Irwin Mitchell.
Ben is not allowed to talk to the media because he remains a serving soldier.
But his mother, Diane Dernie, told the paper she believes there has been "deception" from the authorities.
"Under an agreement reached with us and the NHS in 2016, the MoD is supposed to provide Ben's wheelchairs, prosthetic limbs and specialist medical services not available to us locally on the NHS," she said.
"We have learned, contrary to what the Army has told us, that charities have provided two of Ben's wheelchairs from funds donated by the public. This was a deception on their part.
"We cannot suffer in silence any longer. We need a long-term care plan in place for Ben now."
Mrs Dernie said one of Ben's wheelchairs, which he used between 2013 and 2016, had been provided by Help For Heroes.
"Senior officers suggested to us that they'd provided the chair," she told the paper.
"How could the Army palm off the responsibility for providing it on to a charity? That's not right.
"Then in 2016 they admitted there was no budget for wheelchairs. Ben waited 15 months for a new one, which, as I understand, also came from a charity."
In a statement, an MOD spokesman said: "We can assure Lance Bombardier Parkinson and his family that we are working hard to establish his new care package as quickly as we can.
"We recognise the family's frustrations that the new package hasn't been established earlier, however, given this is a new and innovative scheme we have a duty to make sure it continues to provide the best care possible.
"In the meantime we, along with the NHS, continue to deliver Lance Bombardier Parkinson's day-to-day and specialist care needs."