Lansdowne Oil & Gas announced Monday that it has engaged Diamond McCarthy LLP to pursue its arbitration claim over Ireland’s refusal to award a lease undertaking for the Barryroe oil and gas field.

A funding arrangement has been reached whereby the US law firm will fully fund the costs associated with the claim on a non-recourse basis.

The dispute dates back to an application for a lease undertaking submitted in April 2021 as a follow-on authorisation to an exploration licence in which Lansdowne held a 20 per cent interest, through its wholly-owned subsidiary, Lansdowne Celtic Sea Limited.

Under the terms of the SEL1/11 licence, the licencees say they had the right to progress to a lease undertaking.

However, the application for a lease undertaking was refused by the Irish Department of the Environment, Climate and Communications in May 2023.

In June 2023, Lansdowne gave Ireland notice that a dispute existed under the ECT.

In a statement, the oil and gas company said the agreement with Diamond McCarthy LLP “provides sufficient funds, on a non-recourse basis, to cover legal fees and costs associated with pursuing the claim through to resolution”.

The gross compensation claim is expected to be at least $100 million plus interest. In the event of a successful award of around $100 million, Lansdowne’s share of the proceeds is expected to be between 60 per cent and 70 per cent.

Lansdowne was previously advised on its claim by Mantle Law, a London and United Arab Emirates-based international arbitration law firm with a focus on energy, construction and infrastructure disputes.

Mantle Law and Diamond McCarthy will now “co-counsel to progress the claim to conclusion”.

Stephen Boldy, CEO of Lansdowne, said: “On behalf of Lansdowne and all our shareholders, I would like to thank the legal teams that have worked on our case to reach this substantial funding agreement, which will allow us to proceed to seek just compensation for the loss of our Barryroe asset.”

The Irish government last year announced it would withdraw from the ECT — the treaty being widely criticised by climate justice campaigners — following similar decisions by the EU, UK and other parties.

However, climate minister Darragh O’Brien last week confirmed in the Dáil that Ireland had not yet completed the process of withdrawal.

“The government is committed to exiting the ECT as soon as is practicable and the relevant memorandum is expected to be brought to government in the near future,” he said.

“Ireland is still a member of the treaty and will remain so until we officially leave.

“The modernised treaty provides for less exposure to investor claims than the original treaty, and the modernised treaty is available to view on the ECT website.

“However, the government’s position remains that Ireland will exit the treaty.”

The Department of Climate, Energy and the Environment and the Department of Foreign Affairs and Trade have been approached for comment.