PROVIDING substitute buses for security alerts on the rail network has cost Translink more than £250,000 in the last six years.
Since 2010, there have been 89 incidents of buses having to be provided to transfer train passengers due to suspicious objects left on the rail line.
That means that on average, there has been at least one security alert on the rail line every month for the past six years.
Regional Development Minister Michelle McIlveen confirmed that the cost of offering replacement bus services amounted to almost £270,000.
The number of security alerts on the line which have required a bus transfer has halved from a high of 33 in 2010/11 to just 16 in 2014/15, reaching a low of three occasions so far this year.
The figures were released in response to a question from UKIP Strangford MLA David McNarry, who said that the onus of responsibility lay solely with "the people who cause this disruption".
He said: "Having said that, I don't understand the costs. They seem extremely high to me. At the end of the day everybody is paying for this.
"I have to take my hat off to the public transport providers and staff during the Troubles, but you would have thought that after this time they would have had something much more efficient and cost effective to kick in.
"When the chief constable talks about a lack of resources then these are the incidents he is talking about. Will anybody end up in court for this? Will anybody end up charged? I hope so but I doubt it."
Last week, train passengers travelling through Lurgan were forced to travel on bus services between Portadown and Lisburn due to a security alert, the third time in the space of a month the line was closed.
SDLP East Derry MLA John Dallat said that most cases of disruption had arisen on the Belfast to Dublin service.
He said: "I ask myself again, just as I did in years gone by: 'How on earth can disrupting rail travel between the two parts of Ireland help towards a united Ireland. Clearly not.
"It is, therefore, particularly regrettable that on the cross-border trains we are still dealing with people who don't understand that investing in transport infrastructure is the best way of minimising the disadvantages of partition."
A Translink spokeswoman said that the safety and security of passengers and employees is "our top priority."
She said: "In the case of security alerts on our rail network, we work closely with the PSNI and other relevant authorities and take their guidance in managing the potential impact to our services.
"These are very challenging situations and we work hard to make alternative transport arrangements for our passengers in order to minimise the disruption caused."
