He said it was “scanda-lous” that some protesters behave in a self-indulgent way that has no regard for the rights of others.
It is 10 years since Bord Gáis announced the building of the Corrib gas pipeline, and in 2006 heightened security and escalating protests caused the situation to boil over.
Since then, the policing operation of the project at Bellinaboy has cost the taxpayer at least €14.5m.
The figures, provided by Mr Shatter in response to a parliamentary question, do not include basic salaries.
Costs peaked in 2007 when the bill for overtime, expenses and PRSI contributions came to €4.9m. Last year, the overall cost fell to less than €1m. Overtime since 2006 has cost €9.1m.
Mr Shatter said gardaí could not provide projected costs for future policing operations at the Shell refinery as they arose on a case-by-case basis. He said it was “deeply regrettable” so much Garda resources have to be tied up at the site.
Mr Shatter said: “Gardaí have to respond to protest action in the vicinity of the gas terminal in order to prevent public order offences, to enable persons to go unimpeded to and from their place of work and to enable the construction of the refinery and pipeline to be completed. The level of protest activity fluctuates and as such a projection of likely costs is not possible.”
Mr Shatter said policing was “absolutely necessary” in view of the actions of some of the protesters.
“Many are not from the area and engage in a form of protest tourism and have engaged in acts of public disorder as well as damage to property. Such action cannot be tolerated and the Garda presence is there to prevent it,” he said.
“This requires the expenditure of a substantial amount of taxpayers’ money which could be devoted to far better purposes if it was not for the actions of many of those involved in the protests.”
Sinn Féin TD Jonathan O’Brien criticised the minister, saying it was “wholly unacceptable” to blame the costs on a community who are exercising their democratic right to protest.
“It is somewhat arrogant to suggest that the people engaged in such protests are there as a form of self-indulgent protest tourism,” Mr O’Brien said.
“As if people would risk life and limb where there are extremely heavy-handed gardaí present, for the craic. Time and again there have been questions raised regarding Garda activity in Mayo and no adequate answers have ever been given.
“The fact that the State has paid this enormous amount of money to help Shell to build a pipeline against the wishes of the community is disgraceful, particularly when the minister and the Garda Commissioner are seeking ways to shut down rural Garda stations.”