The possibility of a "no" vote in the Irish referendum on the reforming Lisbon treaty has put pressure on a number of European heads of government, who are keen to see the reforms passed.

French PM Nicolas Sarkozy, whose country will take the six monthly chair of the European Union on July 1, has admitted a negative vote in the Republic of Ireland may derail his country's reform agenda for the EU and has promised a joint response with outgoing president Angela Merkel in the event of such an outcome.