Religion must be given a greater role in public life to push back a wave of "intolerant secularisation", Cabinet minister Baroness Warsi will argue during an official visit to The Vatican.
Warsi, a Muslim, will call for Europe to become "more confident in its Christianity" in a strident defence of faith, backed by Prime Minister David Cameron.
The peer is leading a high-level two-day delegation of seven British ministers to the Holy See, including three of her Cabinet colleagues, which has been granted an audience with Pope Benedict XVI on Wednesday.
Culture Secretary Jeremy Hunt, Secretary of State for Scotland Michael Moore and Northern Ireland Secretary Owen Paterson will also attend, along with International Development Minister Alan Duncan, Energy Minister Greg Barker and Foreign Office Minister Lord Howell of Guildford.
Despite Duncan and Barker being openly gay, the forthcoming free vote in the Commons on introducing gay marriage is said to be firmly off the agenda.
In the first speech to staff and students of the Pontifical Ecclesiastical Academy by an outside minister, Warsi will compare the intolerance of religion with totalitarian regimes.
"In order to encourage social harmony, people need to feel stronger in their religious identities, more confident in their beliefs. In practice this means individuals not diluting their faiths and nations not denying their religious heritages," she will say.
"If you take this thought to its conclusion then the idea you're left with is this: Europe needs to become more confident in its Christianity."
Speaking amid continued fallout over the High Court ruling that prayers cannot be a formal part of local council meetings, she said it was a myth that to protect minorities "we need to erase our religious heritage".
Christian roots "shine through our politics, our public life, our culture, our economics, our language and our architecture", she will argue.
"You cannot and should not extract these Christian foundations from the evolution of our nations any more than you can or should erase the spires from our landscapes."
Quoting the Bible, she will praise the role of the Catholic Church in toppling communism, securing peace in Northern Ireland and responding to natural disasters across the world.
The Pope had been right to warn, in a speech in Westminster Hall during his state visit to the UK last year, against an increasing marginalisation of religion," she will say.
"I see it in United Kingdom and I see it in Europe. Spirituality, suppressed. Divinity, downgraded.
"Where, in the words of the Archbishop of Canterbury, faith is looked down on as the hobby of 'oddities, foreigners and minorities'. Where religion is dismissed as an eccentricity because it's infused with tradition.
"Where we undermine people who attribute good works to their belief and require them to deny it as their motivation.
"And where faith is overlooked in the public sphere with not even a word about Christianity in the preface of the European Constitution.
"Our response has to be simple: holding firm in our faiths, holding back intolerant secularisation, reaffirming the religious foundations on which our societies are built and reasserting the fact that, for centuries, Christianity in Europe has been inspiring, motivating, strengthening and improving our societies.
"Politicians need to give faith a seat at the table in public life.
In an article for the Daily Telegraph ahead of the visit, she wrote: "For me, one of the most worrying aspects about this militant secularisation is that at its core and in its instincts it is deeply intolerant.
"It demonstrates similar traits to totalitarian regimes - denying people the right to a religious identity because they were frightened of the concept of multiple identities."
Baroness Warsi has regularly spoken out about the need to reassert religious influence on public life, and insisted in a speech on the eve of the Pontiff's visit last year that the coalition Government "does God".
In a rare foray on to the issue by a prime minister, David Cameron recently urged the Church of England to lead a revival of traditional Christian values to counter the country's "moral collapse".
Deputy Prime Minister Nick Clegg is atheist.
The visit has been arranged to mark the 30th anniversary of the establishment of full diplomatic relations between the UK and the Holy See.
They will hold talks with Vatican officials on topics including inter-faith dialogue, human rights, environment and climate change and international development and are being lodged within the tiny city state.
However the visit comes after a poll of British Chrisitans, which suggests most feel religion should have no place in public life.