Minister for Education Batt O'Keeffe has written to schools asking them to prioritise newly qualified teachers for substitute work.
The Minister's letter comes amid concern at the number of retired teachers taking up substitute work.
Figures released to Fine Gael education spokesman Brian Hayes show that almost 2,000 retired teachers worked in primary and secondary schools last year while receiving a pension.
However, the Irish Primary Principals' Network has taken issue with Mr Hayes, saying his figures refer to the last school year before the education cuts.
It says that principals throughout the country were actively engaged in sourcing newly qualified graduates for substitute positions in schools.
The network also said that principals only resort to employing retired teachers when no newly trained ones were immediately available.
The figures were supplied by the Department of Education in response to a parliamentary question tabled by Mr Hayes.
They show that around 2,000 retired teachers, who are in receipt of pensions, were still working as substitute teachers, at both primary and second-level schools last year.
Around 1,500 of them were working in primary schools at a rate of €206 a day, while the remainder were earning €49.60 per hour in secondary schools.
Mr Hayes said that an employment programme should be put in place to help teaching graduates.
He said Ireland is losing hundreds of young teaching graduates to New Zealand, Britain and Australia.
Mr Hayes urged Minister O'Keeffe to free-up all casual and substitute teaching hours for younger, qualified teachers who are unemployed.
He has also called for the establishment of a graduate teacher recruitment scheme, dedicated to employing young teachers as teaching assistants at a special, reduced rate of pay.
The department said that the employment of teachers is a matter for each school's management authority.
Speaking on RTÉ's Morning Ireland, incoming INTO General Secretary Sheila Noonan said far fewer retired teachers were working as substitutes this school year.