The Minister for Justice, Equality and Law Reform, Mr McDowell, has told new members of the Garda "not to compromise on standards and integrity" in the course of their duty.
The Minister also defended Garda manning levels, spoke of relieving gardaí of peripheral duties and having the speed camera system staffed entirely by civilians.
In an address to 119 gardaí graduating from the Garda Training College in Templemore, Co Tipperary, yesterday, Mr McDowell said they should ignore "those cynical and tired voices" who claimed high standards of professionalism could not be upheld in the real world.
"There may be people who denigrate An Garda Síochána from outside but I want to say this to you, the greatest critics of An Garda Síochána should always be from within."
The Garda Commissioner, Mr Noel Conroy, who was attending his first graduation ceremony with the Minister, also emphasised the need for discipline in the force.
With police work "open to scrutiny more than any other type of activity", gardaí must ensure they used their powers appropriately and with sensitivity, he said.
Yesterday's graduates bring to 11,908 the current strength of the Garda. Mr McDowell said he intended to bring the numbers to an "all-time high" of 12,200 over the next 14 months. The Government's commitment to a further 1,800 gardaí remained, and "if the resources are available it is my intention to press for them to be applied to expand An Garda Síochána as soon as we can".
In the meantime, he said, there was potential for better utilisation of Garda time by removing gardaí "from peripheral, marginal policing activities which happens at the moment".
He said he was working with the Minister for Transport, Mr Brennan, to have speed cameras operated entirely by non-Garda personnel, "and there are many other opportunities for concentrating gardaí on core duties".
On this week's difficulties in obtaining a jury for gangland-related criminal trials in Limerick, the Minister said the decision to locate such trials in the city "hasn't backfired. The Central Criminal Court has gone to Limerick in order to bring justice to the community and that initiative is going to be carried on.
"It may be that individual trials may have to be held in different parts of the country for different reasons. But in general I strongly support the judiciary in their determination to bring justice to the people rather than have it happen at a remove."
Five members of the Garda were awarded Scott Medals for bravery at yesterday's ceremony. Gold and silver medals were awarded respectively to Trainee Garda Colm Finnerty, Co Roscommon, who rescued three men from the River Liffey last December; and Garda Raymond Costello, Cork, who was involved in an attempted water rescue in January 2001 in hazardous conditions.
A bronze medal was awarded to Det Garda Kieran McNamara, Co Clare, who disarmed a bank raider carrying a knife in a theft at Loughrea, Co Galway, in March 2002. A further bronze was awarded jointly to Garda Gerard Collins and Garda Darran Kirwan, both based at Dundalk Garda station, for rescuing a man who jumped into Castletown River in January 2002.