The controversy over the removal of a medieval walled ditch at Carrickmines Castle in south Co Dublin is to be raised in the Dáil today by Green Party TD Mr Ciarán Cuffe.
Mr Cuffe said that the dispute over the validity of an excavation licence for the work had brought the Department of the Environment and the Department of Arts, Sport and Tourism "into direct conflict".
"I will be asking the Taoiseach to clarify both the role of Dúchas [the Heritage Service\] and the very public row between two of his Departments," he said.
Dúchas, which falls under the remit of the Department of the Environment, issued an excavation licence for the work, but this has been objected to by the National Museum of Ireland, which falls under the remit of the Department of Arts, Sport and Tourism.
Dr Seán Duffy, chairman of the Friends of Medieval Dublin, said that the matter had produced "a crisis at the heart of the Cabinet".
A spokesman for Dúchas rejected the claim that two Departments were "at loggerheads" over the issue. "That's not the case at all," he said. "We are happy that the correct procedures have been followed in issuing the licence."
Work began at the weekend on the removal of the revetted fosse, or walled ditch. This is the last archaeological excavation before construction workers move in to prepare the site for construction of the South-Eastern Motorway. The removal of the fosse is painstaking and will take several days, according to Dún Laoghaire-Rathdown County Council.
Mr Eamonn O'Hare, the council's director of transportation, said that the work involved taking drawings and photographs of the wall as well as cleaning the stones and removing them one by one. The fosse would then be re-created elsewhere. He repeated his assertion that the licence was valid and said that the National Museum had been consulted.
The National Museum's keeper of antiquities, Mr Eamonn Kelly, has meanwhile repeated his belief that the licence was not valid because the museum was not consulted. "Absolutely nothing has happened to change that situation," he said.
The National Monuments Act specifies that an excavation licence can only be issued after consultation with the National Museum.
Meanwhile, Mr Proinsias De Rossa MEP said he believed that there had been a breach of the environmental impact assessment directive. If this was found to be so, EU co-funding of up to €75 million could be withdrawn and the Government could be heavily fined.
This morning, two conservationists will seek a Supreme Court hearing of their appeal against a High Court decision which rejected their request for an injunction to halt work at the site.
Mr Vincent Salafia, spokesman for the Carrickminders group, which is opposing the routing of the motorway, said that the council had been informed of the group's intention to lodge an appeal. He added: "So it is a matter of great concern to us that they are proceeding with work while they are under notice of the appeal."
Gardaí were called to the site twice over the weekend after Mr Kelly of the National Museum claimed that the work was illegal. It is understood that gardaí have sought clarification on the legal issues raised. A Garda spokeswoman said that nobody had been charged with any offence.