Sinn Fein chief O'Neill in challenge to EU City of Culture ban
Michelle O'Neill has written to the European Commission challenging its decision to ban Belfast and Londonderry's joint bid to be named the European Capital of Culture.
British entrants for the 2023 honour have been deemed ineligible because the UK will not be part of the European Union or European Economic Area by then.
Sinn Fein's Stormont leader said: "I consider the position being adopted by the EU Commission to be politically punitive and am concerned at the precedent it may now set. It is unacceptable."
Last week DUP MEP Diane Dodds described the move as "needless and spiteful posturing by the Commission".
MPs representing the five UK areas which have submitted bids for culture capital status have also urged Commission President Jean-Claude Juncker to allow the process to continue.
They told him: "We find it inexplicable that the European Union waited until after the bids from the United Kingdom had been submitted before ruling them all ineligible, when it has been aware of the UK's decision since June 2016.
"Politics should not interfere with what is in many ways an event intended to bridge cultural and political divides."
Five different UK bids were competing to host the 2023 European Capital of Culture, spending hundreds of thousands of pounds on their entries.
Nottingham, Leeds, Milton Keynes and Dundee were also in the running for the accolade, which has the potential to provide a major economic boost.