Gay rights campaigners are to hold a rally outside Buckingham Palace on Monday to call for the right to marry.
The midday event, organised by Peter Tatchell, will see activists attempt to deliver a wedding card to Kate Middleton and Prince William to ask them to support marriage equality.
Mr Tatchell said: “Our event will urge the royal couple to support moves to end the ban on gay marriages. We want equal marriage rights for all couples, regardless of sexual orientation. It is our hope that they might be the first royal couple to express support for marriage equality.
“William and Kate are a modern young couple. I am sure they have gay friends and would not wish to see them discriminated against.”
Mr Tatchell is leading the Equal Love campaign, which is pursuing full marriage equality at the European Court of Human Rights.
The case involves four gay couples barred from marrying and four straight couples barred from civil partnerships.
PinkNews.co.uk understands that the Liberal Democrats in government and increasingly Tories in the centre – including David Cameron – are minded towards full marriage equality.
An amendment in the Equality Act will give gay couples the right to have civil partnerships in religious buildings and ministers hope this provision will be enacted by the end of the year.