It says that Orthodox voices will be louder because both nations have growing populations which boost its adherents, according to analysis in the Greek VIMA newspaper.
But at the same time their entry will highlight divisions within Orthodox ranks, because the Romanian patriarchate is preparing to open its own office in Bucharest.
Since Poland joined the EU in 2004, up to two million citizens have left the country, fleeing from the 18 per cent unemployment in the country and seeking career opportunities abroad. In the past three years, Poles have strengthened the churches in Britain. There are already more than 100 Polish priests working in England and Wales.
Scenes of celebration were seen across Romania and Bulgaria as the countries greeted the New Year, marking their accession to the European Union, and 17 years since the fall of communism.
Across the two capitals, Bucharest and Sofia, more than ten thousand people were reported to have attended concerts to rejoice at the newly found status their countries have been given.
The president of Romania, Traian Basescu, addressed the crowds, saying that EU entry was an "enormous chance for future generations".
He said, "It was hard, but we arrived at the end of the road. It is the road of our future. It is the road of our joy. We arrived in Europe. Welcome to Europe," Basescu said.
The EU now increases to 27 members, and surpasses more than half a billion people.
Prior to the speech, the EU flag was raised outside the government HQ in Bucharest as the European anthem, Beethoven's Ode to Joy, was played.
In Sofia, a pyramid of light illuminated the sky, with rays emanating from the city's Orthodox cathedral, its Armenian church, a synagogue, a mosque and another church. Fireworks lit the sky over the building where the Communist Party once held its HQ.
Bulgarian President Georgi Parvanov gave an emotional speech to the nation, calling the country's EU entry a "heavenly moment".
"The day we are welcoming - 1 January 2007 - will undoubtedly find its place among the most important dates in our national history.
"But let's make it clear, our future success as a nation depends not on European funds and resources, but on our own work."
The two new countries will now come under strict monitoring rules, with many analysts saying there is a risk that EU aid will be mis-spent, or just not taken up because the countries' institutions are too disorganised.
