The British government spent more than £4 million (€4.5m) defending a former army veteran acquitted of murder in relation to the events of Bloody Sunday.
Soldier F was found not guilty of two counts of murder and five of attempted murder in Derry on 30 January 1972.
His trial concluded earlier this month.
A judge ruled that the statements of two fellow soldiers introduced as a key plank of evidence by the prosecution could not be relied on.
The costs emerged in a parliamentary answer to a question asked at Westminster by Foyle MP Colum Eastwood.
Mr Eastwood described the expenditure as "sick".
Armed Forces Minister Alistair Carns confirmed that £4.3m had been spent - much of it in legal fees linked to the case.
They date back to 2019 and include money spent on an associated judicial review of an earlier decision to drop the criminal charges against Soldier F.
Mr Carns said the costs could rise "marginally" once the final legal bill was received.
Other money was spent on flights, accommodation, and pastoral support for the former paratrooper.
Mr Eastwood said the findings of the Saville Inquiry were clear on what Soldier F had been responsible for on 30 January 1972.
"Soldier F came to Derry as part of a regiment that shot and killed innocent civil rights protestors as they ran for their lives.
"He is a self-confessed killer and yet for more than 50 years, he has been a protected species in the eyes of the British government."
13 civil rights protesters were shot dead in Derry on Bloody Sunday. A 14th died later of his injuries.
At least 15 others were injured by the gunfire. The Saville Inquiry found that the soldiers had lost control when they opened fire on unarmed civilians.
