The European Commission was on Thursday under fire from Irish opponents of the Lisbon treaty over its approval of a €55m ($81m) grant to the Polish factory of Dell, the US computer company.

The Commission’s decision to give the go-ahead for Polish government aid under the state aid rules was seen as “a slap in the face” for Irish workers laid off when Dell relocated from Limerick to Poland last January. The announcement comes just a week after Jose Manuel Barroso, the Commission president, was in Limerick announcing a €15m aid package to help the Irish workers – a move which at the time prompted accusations he was seeking to “buy” Irish votes ahead of the October 2 referendum on the Lisbon reform treaty.