Mona Costelloe - Partner

Mona Costelloe 2012



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+353 1 691 5010
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Mona Costelloe is a Partner in the Commercial Litigation Department and advises a wide range of national and international clients on complex litigation issues including financial services litigation, breach of contract and tortious claims, professional negligence, property disputes, product liability and sale of goods claims and contentious construction disputes.

Mona represents clients in all Court jurisdictions with particular expertise in the Commercial Court. She advises and represents clients in Alternative Dispute Resolution process including conciliation, mediation and arbitration and is proactive in attempting to achieve early dispute resolution.


Recent Experience

  • Representing group of pension scheme members in Commercial Court and Court of Justice of European Union proceedings on the alleged failure of the Minister for Social and Family Affairs to adequately transpose the provisions of European insolvency directives concerning the protection of employees and their pension entitlements in the event of a double insolvency.  Case is currently before the Court of Justice of the European Union;
  • Advising the Lead Plaintiff in a US Securities Class Action claim for substantial losses incurred through investment in an Irish based UCITS fund vehicle arising from the collapse of Bernard L. Maddoff Investment Securities.  Advices are on a wide range of matters of Irish law including the UCITS Regulations, the duties of the custodians and sub-custodians, forum non conveniens, the rule in Foss v Harbottle and potential claims of the Class in Ireland. Representing interests of the Lead Plaintiff as a Notice Party in related Irish Commercial Court proceedings.  
  • Represented subordinated bondholder of Allied Irish Banks, plc ("AIB") in High Court proceedings involving a unique form of statutory review to set aside a Subordinated Liabilities Order ("SLO") made in respect of the subordinated debt of AIB under the Credit Institutions (Stabilisation) Act, 2010 ("CISA").   Advised on a wide range of matters concerning the subordinated liabilities of AIB and the provisions of CISA.  Dealing with a variety of issues such as the degree of burden sharing imposed on the subordinated liabilities of AIB, the necessity of the SLO, the position of bondholders in the event of a winding up, the alternatives to an SLO and EU law and constitutional law issues.  The proceedings were resolved in July 2011, after 16 days of hearing, and brought about amending legislation enacted in October 2011 under the Central Bank and Credit Institutions (Resolution) Act, 2011.
  • Advised committee of international subordinated bondholders of Bank of Ireland, in conjunction with team of foreign lawyers from USA and England, on the provisions of the Credit Institutions (Stabilisation) Act, 2010 and the amendments introduced under the Central Bank and Credit Institutions (Resolutions) Act, 2011.  Advised on the potential for and implications of an application for a Subordinated Liabilities Order ("SLO") by the Minister for Finance. Advised on constitutional and EU law issues. Drafted Submissions on behalf of the committee following invitation for submissions from Minister for Finance in respect of a possible SLO for Bank of Ireland.  The Minister for Finance ultimately decided not to apply for an SLO.
  • Senior member of a specialised Commercial Court team in the first case in Ireland concerning damage to houses due to the swelling of pyritic infill.  The proceedings were at hearing for 150 days in the Commercial Court and also concerned over 600 associated High Court homeowner claims.  Ultimately the matter concluded in a settlement with both the Commercial Court defendants and the homeowners (represented by 46 separate law firms) after a lengthy mediation process


  • Law Society of Ireland, Admitted as a Solicitor Hilary Term 2003
  • Masters of Law (LL.M) Trinity College Dublin, 2000
  • BA, Law and European Studies, University of Limerick, 1999


  • Dublin Solicitors Bar Association
  • Law Society of Ireland
  • Association of Regulatory & Disciplinary Lawyers
  • Commercial Litigation Association of Ireland


  • Newly promoted partner Mona Costelloe is‘highly professional and a delight to deal with’. - Legal 500, 2014
  • Mona Costelloe is 'particularly impressive' - Legal 500, 2013
  • Awarded Law Society Conveyancing Prize, 2001
  • Mona has presented internal and external seminars and has previously lectured law modules in Dublin City University and Dublin Institute of Technology