The defunct Northern Ireland Assembly is spending £360,000 (€400,000) on policing services every year.
Devolved government has not sat at Stormont in almost two years, but PSNI officers are on duty at the building every day.
The powersharing government collapsed in January 2017 following a breakdown in relations between the Democratic Unionists and Sinn Féin.
Many of the 90 MLAs who were elected to the Assembly in 2017 still use their offices in the building.
However, the debating chamber has remained silent apart from visitor tours for almost two years.
There has been a police presence at Stormont since 2007, when Loyalist killer Michael Stone burst into the building and attempted to launch an attack.
Responding to a Freedom of Information Act request from the Press Association, the Assembly Commission said it spends £360,000 per annum on policing services at the North's Parliament Buildings.
They declined to say how many officers are involved in the work, but most days two are visible on duty at the front door of Parliament Buildings.
The TaxPayers’ Alliance has questioned the use of public money.
“Given there hasn’t much political action in Stormont for a while, taxpayers will wonder how this bill is quite so large,” said John O’Connell, chief executive of the TaxPayers’ Alliance.
“Some protection is no doubt needed at all times but it’s important to get the balance right and think about those picking up the tab.
“When budgets are tight, it’s crucial to get maximum value for taxpayers’ money.”
A spokeswoman for the Northern Ireland Assembly said it has a responsibility to protect the safety of all the building users.
“While the Assembly is not currently sitting, Parliament Buildings remains fully operational for MLAs, their staff, Assembly Commission staff, visiting dignitaries and members of the public who visit the building to take part in tours and a range of charity functions and events,” she said.
“As such the Assembly Commission has a responsibility to ensure that the appropriate security mechanisms and personnel are in place to protect the safety of all building users.
“A police presence has been in place at Parliament buildings since 2007, and the retention of this service is consistent and in line with the security procedures employed by other legislatures.
“The Assembly Commission regularly monitors and reviews the level and appropriateness of its security measures to ensure that they are proportionate, fit for purpose and provide value for the public purse.”
- Press Association