The Palace of Westminster is among dozens of public buildings across the country which will be brightly illuminated next Wednesday evening for the #RedWednesday initiative.
Other landmarks taking part include cathedrals in Ayr, Edinburgh, Paisley, Birmingham, Norwich, Wrexham, Derry and Armagh.
#RedWednesday is organised by Aid to the Church in Need (ACN) and Christian Solidarity Worldwide (CSW), two organisations which advocate from Christians around the world who live under pressure for their faith.
The speakers of the House of Commons and the House of Lords both agreed that Parliament support the campaign, as it did last year.
Trevor Harrison from Sevenoaks in Kent lobbied his local MP, Sir Michael Fallon of the Conservative Party, to endorse #RedWednesday.
He was quoted by ACN as saying: "Turning Parliament red is a wonderful way to get the message about religious freedom to as wide an audience as possible."
"We all need to get behind #RedWednesday - we need to stand together against violence carried out in the name of religion - we need to speak up about regimes which persecute people of faith."
A solidarity service outside Westminster Cathedral at 6pm will feature speeches by Coptic Orthodox Bishop Angaelos, National Director at ACN UK Neville Kyrke-Smith and Chief Executive of CSW Mervyn Thomas.