French opponents of plans to legalise same-sex marriage in their home country have invited Brits to protest alongside them in London's Trafalgar Square.
The rally will take place at the same time as a major demonstration planned in Paris in opposition to the French Government's plans to redefine marriage.
The last Paris rally in January saw around a million people turn out onto the streets of Paris in opposition to the plans.
At the same time, around 600 French residents living in London protested outside the French Embassy.
The UK-based protesters are inviting Brits to join them in Trafalgar Square for the protest on Palm Sunday.
The London rally takes place from 2pm to 5pm and is being supported by Christian Concern and Anglican Mainstream as a "visible sign against the sterile adult-centred nature of same-sex marriage".
London co-ordinator Damien Fournier Montgieux, said: "Almost out of nowhere we are suddenly faced with a huge challenge to the future of marriage and the family in both France and the UK. There has been no warning or consultation with the people.
"It is children and the future generations that will suffer most as a result of these unjust changes. I believe that gay people's request is sincere but children's rights and freedoms are too often forgotten in this debate about the 'rights of adults'.
"For the sake of children, we must act quickly and I would encourage all those in the UK who are concerned about changes here in the UK or in France to join us on Sunday. This is now a pan-European challenge and it needs a pan-European response."