Jan 17 (Reuters) - British engineering firm GKN Holdings is facing potential enforcement action by some holders of its euro medium-term notes (EMTNs) programme worth 2 billion pounds ($2.45 billion) after concerns over the company's conduct related to the notes.

An ad hoc group holding over 72% of the EMTNs in a letter dated Jan. 16 to GKN said it was concerned by how the engineer conducted a tender offer without informing it of an "event of default" following the proposed separation of GKN Automotive and GKN Metallurgy.

GKN's parent Melrose Industries and GKN did not immediately respond to requests for comment. ($1 = 0.8151 pounds) (Reporting by Sinchita Mitra in Bengaluru; Editing by Maju Samuel)