Demonstrators protested outside Hampton Court Palace on Tuesday after its Chapel Royal held its first Catholic service in more than 450 years.
Organised by the Protestant Truth Society, a small group of protestant clergy led the protest on Hampton Court Bridge as the service took place.
About 300 people attended the service, which was conducted mostly in Latin and concluded with the national anthem.
But outraged Protestants held placards and spoke against the service on a microphone.
Teddington’s Christ Church pastor Reverend Dominic Stockford, who was a candidate for the Christian Party in May’s General Election, was one of demonstrators.
He said: “We felt it was necessary to make a statement at the Chapel Royal because a statement was being made by those holding the service.
“We felt we needed to stand and speak because of the significance of the palace and because it was portrayed as a wonderful, uniting occasion.”
He said the protest “went well” and that his group did not meet any “unpleasant opposition”.
The Rev Stockford added: “It is a matter of eternal life and how we get eternal life with God so this is a matter of the utmost importance.”
The group held up signs carrying slogans including ‘The Church of England is denying its own faith!!!’ and ‘Reversing the Protestant Reformation means abandoning the Bible’.
Reverend Peter Simpson said: “The Church of England was founded upon the truth of the scriptures.
"Indeed, the very first bishops of the Church of England were burnt at the stake because they refused to compromise on the truth of God’s word."
It was announced last month that the palace’s Chapel Royal would host its first Catholic service since the Reformation.
The service represented an unprecedented coming together of the Catholic and Anglican churches, organised jointly by the Choral Foundation and the Genesis Foundation.
Michele Price, from the Choral Foundation, said: "Tuesday evening’s event and the fact that it has attracted interest from all over the world, shows the significant role that Hampton Court plays in our country’s heritage.
“Faith and the crown once again placed it firmly in the forefront of minds spiritually, musically and as a seat for history-making."
Richmond and Twickenham Times readers were not impressed with the protest held to coincide with the event.
Lynne Walsh said: “If they had that spare time, they could have helped in a food bank, hostel or day centre.”
Caroline Wadsworth wrote on Facebook: “Outrageous, 21st century, supposed to be sympathetic to one & all, don't people ever learn from past mistakes. Do we not have enough wars on our hands?”
Twickenham MP Tania Mathias said: “I have supported and attended interfaith services in the past and I am glad that Hampton Court Palace will host inspiring leaders of both the Catholic Church and the Church of England in the same service.
“The Chapel Royal has great history and I hope that this will be a peaceful and important occasion for our area.”
The service was recorded for BBC Radio 3 and will be broadcast on March 30 at 3.30pm-4.30pm.