MINISTER FOR Transport Noel Dempsey strongly defended the Government's proposed north Dublin metro line linking the airport and Swords to the city centre.

"The investment involved in Metro North should not be considered in the light of the 30-year period during which we will pay for it under the public-private partnership, but in the light of the fact that the system will serve the needs of the people for 50 or 100 years," he said.

Mr Dempsey said that he had heard much "ignorant comment" about Metro North and questions as to why buses should not be acquired.

"To do what we want with Metro North, that is, to move approximately 20,000 passengers in each direction during peak travel times, we would have to invest in approximately 400 to 500 buses," said Mr Dempsey.

"There would not be sufficient road space to do so." In opting for a Luas solution, as some people were advocating, the maximum number of passengers accommodated would be about 8,000 per hour at peak time.

"Given that the population is to grow by approximately 500,000 . . . by 2015-16, a Luas or totally bus-based system of public transport in the north county Dublin area is a nonsensical proposition," said Mr Dempsey.

The Minister said that the Railway Procurement Agency, which was responsible for the project, had applied last month to An Bord Pleanála for a railway order for Metro North.

The application clearly set out the route alignment, underground and surface sections and station locations, he said. The public-private partnership tenders were due to be submitted to the agency in early February.

Once the procurement and the statutory approval processes were completed, the Government would make a final decision.

"This is a long-standing requirement for all very large projects under Transport 21," he added.

Mr Dempsey said that next year's estimates included substantial funding provision for those works.

Minister for Education Batt O'Keeffe said that from next January substitution cover for uncertified sick leave in all schools, and for official school business in post-primary schools, was being suspended.

He was asking schools, he said, to consider carefully the necessity for absences at events outside school which took place during core class contact time.

Mr O'Keeffe said that substitution cover would still be paid for all other categories of teacher-absence currently provided for and the 37-hour scheme of payment to teachers for supervision and substitution would continue.

He added that there would be rationalisation of in-career development courses for teachers next year.

"However, we will continue to provide a wide range of courses for teachers in key areas including special education and language support," he added.

The Minister said he had also regularised an anomalous situation whereby fee-charging schools under Catholic patronage were not receiving certain grants paid to other fee-charging schools.