Irish premier Enda Kenny has urged Britain to remain within the European Union.
The Taoiseach, in London for a series of engagements including talks with Prime Minister David Cameron, insisted Britain has much to gain from its membership.
"We see the British relationship with the EU as being a two-way relationship - Britain benefits from its membership of the EU, and the EU is better off with Britain as a leading member making a valued contribution," Mr Kenny said.
Ireland is more than half way through its six-month EU presidency term. Its time at the helm also marks the 40th anniversary of both Ireland and Britain joining the EU.
Mr Kenny said while the country's future is closely tied with Europe, its connection with Britain - its "nearest neighbours" - was stronger than ever.
Speaking during a whistle-stop trip to London, the Taoiseach insisted both nations were like-minded on numerous European issues such as the single market and trade.
He made the comments at a business event at the city's Mansion House, where he also vowed that Ireland would act impartially during negotiations on the controversial financial transactions tax. He said the state would use its position as EU president to facilitate the discussions, but would strike a careful balance in respecting both sides of the debate.
Later, during a lunch at the British-Irish Chamber of Commerce at Savoy Place, Mr Kenny said Ireland looks to the British market as a place where its business could contribute to the state's national recovery. "For our part, Britain is our biggest market for key sectors such as food and beverages, and of course for tourism," the Taoiseach said.
In an address to the London School of Economics later, Mr Kenny said Ireland and Britain had travelled a long distance together within the EU.
The Taoiseach said: "The UK is an enormously important partner for us in Europe. We greatly value the contribution you make, and we look forward to it continuing long into the future. It is good for Europe, good for Ireland and, not least, good for the UK."