Fine Gael has claimed that two thirds of serious crimes committed in the Dublin region last year went undetected by gardaí.
According to the party's deputy leader, Richard Bruton, figures also show that the number of serious crimes committed in the capital rose by nearly 7,000 over the past five years.
The figures were gathered by Fine Gael from the Garda Síochána Annual Report and the Department of Justice.
According to the figures, the number of serious crimes committed in the Dublin Metropolitan Region rose from 38,000 in 2000 to just under 45,000 last year.
The number of homicides rose from 18 to 72 and the number of assaults doubled in that period.
According to Fine Gael, the detection rates have fallen in all ten categories of serious crime since 2000.
Mr Bruton says the overall detection rate for serious crimes in the capital stands at 33.5%.
He says the figures show that the Minister for Justice, Michael McDowell, has failed in his primary function to protect citizens.
However, a spokesperson for the Department of Justice said the figures compare well with those from other jurisdictions, in particular the detection rates for homicides and robberies.
The spokesperson also said one of the functions of the newly established Garda Inspectorate will be to look at detection rates in the capital to ensure they are in line with the rest of the country.
