AN Bord Pleanala may not make a decision on the Lisheen lead zinc mine proposal until May 31st. But despite the delay, objectors will not be called before an oral hearing, it emerged last night. The bord said no one had requested such a hearing.

In a letter sent to Ivernia and Minorco, the mine's developers, as well as to several local people who have objected to the project on environmental grounds, An Bord Pleanala said it might need until the end of May to make up its mind.

It said that "numerous issues which are particularly complex" were involved in granting or denying permission for the £120 million development, and this was responsible for the delay.

Also, the letter continued, it was necessary for An Bord Pleanala to cross circulate the relevant documents in accordance with notices served under section nine of the 1992 planning legislation.

A delay of this length is permitted under the law, planning specialists said last night, but is extremely rare.

The bord's letter added that it had considered whether an oral hearing would be necessary to decide the issue, and had determined that it would not.

A spokesman for An Bord Pleanala accepted last night that planning appeals in the past for mining projects had involved oral hearings, but said that even when there was a direct request from appellants for an oral hearing, these were rarely granted.

"I can confirm that an oral hearing was not requested in this case, and an oral hearing will not be held," the spokesman said.

Last August, Tipperary County Council approved the development, which Ivernia and Minorco say will generate more than 700 jobs in the two year construction period and at least a further 300 in the mine's 14 year life cycle.

Local people made four separate objections to the appeals board, all on environmental grounds.

Over the weekend, Minorco's managing director, Dr Graham Rees, said that his company would not, at any rate, be ready to start construction work until the start of March.

In a statement last night, Ivernia and Minorco said they still wanted to begin building the mine by that date, and would prefer An Bord Pleanala to have made its decision by then.

"The partners are pleased that the appeal can be resolved without the necessity for an oral hearing and are still hopeful that the appeal can be determined early enough to allow construction to commence on target in March 1997," a spokesman said.

Industry sources said the two firms would have been very happy with the decision not to have an oral hearing, because some analysts would interpret this to mean that An Bord Pleanala believed there were no insurmountable problems to the project.