It may look like any other agricultural shed, but a building in Monaghan is being rented by the Irish government at a cost of €542,000 over 25 years to store electronic voting machines with a lifespan of just 20 years.

The building, which costs about €21,685 a year to rent, is owned by Martin Duffy, a nephew of Josephine Duffy, the county registrar and returning officer, who was responsible for finding storage for 288 machines and overseeing their upkeep.

The tender for the property in Scotshouse was awarded to Duffy after five other bids were rejected as being unsuitable.

It is understood a consultant’s report, which the Department of Environment has refused to release under the Freedom of Information Act, has raised concern about the cost of this contract.

It is unlikely this building would be worth as much if rented commercially on a normal basis. A search of commercial property websites this weekend found a 2,400 sq feet warehouse in Monaghan available for €780 a month. Even adding in costs for heating and security the annual bill of using such premises would be significantly less than the €21,685 the Scotshouse arrangement cost the state last year (the figure varies from year to year due to the cost of heating).

Since 2007 4,762 of the 7,504 electronic voting machines purchased by the state in 2002 for €52m are being housed in Gormanston army barracks in Co Meath.

A total of 2,742 are still in storage in 13 counties throughout the country at an annual cost of €202,000, including the 288 in Scotshouse. The Monaghan lease is the longest by 15 years and is the fifth most expensive.

The storage of machines in Kerry, for example, is more costly at €31,875 a year but a contract has only been signed for 10 years.

In Monaghan, the government must pay for security and heating, but it is understood Duffy’s “profit” is at least €15,000. The building is fitted with a monitored alarm.

Josephine Duffy refused to comment other than to say that there was no conflict of interest in the awarding of the contract to her nephew as she was “not directly involved” in completing the deal. She said the five tenders rejected did not meet the requirements for the storage of the machines.

“I used an auctioneer to find storage locations and the contract was drawn up between solicitors,” she said.

Duffy added that any other questions relating to the length of the contract was a matter for the environment department and that she was prevented from commenting further.

A spokesman for the department, however, said the storage contract was overseen by Duffy and was her responsibility. According to the department all returning officers undertook the task of finding suitable locations for the voting machines in their constituency and set up the contractual arrangement themselves.

It is not clear whether or not there is an opt-out clause that the state could use to end the storage arrangement nor how much this would cost. The Department of the Environment would not comment on this saying it was a matter for Duffy and her nephew.

When the state moved 60% of the voting machines to Gormanston at a cost of €328,000, it ended a number of storage contracts. It has since indicated that to end some arrangements entered into by returning officers would require large severance payments.

Phil Hogan, the Fine Gael spokesman on the environment, said it was “completely irresponsible” of the state to enter into such costly and long-running contracts for storage of electronic voting machines, particularly ones that may not be value for money.

“This is one of many examples of the cosy arrangements Fianna Fail ministers have allowed to happen in recent years. It was a crazy idea to enter into a 25-year lease on a building for machines that only lasts 20 years,” he said.

Hogan called on John Gormley, the Green Party leader and current environment minister, to end the storage contracts as quickly as possible or to find a way to lower their cost.

The state is also paying €87,000 a year to insure the voting machines. Gormley recently wrote to members of the Greens’ parliamentary party advising them that the electronic voting system, introduced when Martin Cullen, the Fianna Fail TD was minister for the environment, will never be used and should now be disposed of to cut losses to taxpayers.