Soldier F faced charges of murdering James Wray, 22, and William McKinney, 26, as well as five charges of attempted murder.
He was found not guilty at Belfast Crown Court earlier this month.
Thirteen people were shot dead and at least 15 others injured on 30 January 1972 at a civil rights demonstration in the Bogside area of Londonderry.
Veterans minister Alistair Carns gave details of the Soldier F costs in response to a written question from Eastwood.
He said the Ministry of Defence is “committed” to supporting veterans, and that Soldier F had received legal and welfare support throughout proceedings.
Carns added the expenditure dates from March 2019, when the former paratrooper was first charged.
They also include costs associated with judicial review proceedings.
Eastwood said: “In spite of the clear conclusions of Lord Saville, the British Government has spent £4.3m of our money to defend Soldier F over the last six years.
“The premium that is placed on defending soldiers is an insult to victims who are left to fight for truth and justice alone.
“It is sick.”
