Gay couples will finally win the right to marry, Downing Street insisted last night, despite an escalating campaign of opposition led by a former Archbishop of Canterbury and some Conservative MPs.

Lord Carey provoked an angry backlash from gay couples and campaigners as he denounced the move as a "hostile strike" on the traditional view of marriage. There will now be a furious battle ahead of this spring's Queen's Speech, in which proposals could be announced, with the aim of the first gay weddings taking place by 2015 at the latest.

Tory right-wingers gave their backing to a new pressure group, Coalition for Marriage, which accused the Government of having no mandate for the move – and claimed the public was on its side.

But Downing Street insisted that David Cameron remained determined to end the discrimination faced by homosexual couples. A senior source said: "Nothing has changed on this as far as he is concerned. He is very passionate about this subject – it is something that has defined him."

The Home Office begins a consultation next month on how gay couples can be given the legal right to marry in a civil setting such as a register office. Lynne Featherstone, the Equalities Minister, told The Independent: "This Government is promoting a fair society where people respect each other.

"I believe that if a couple love each other and want to commit to a life together, they should have the option of a civil marriage, irrespective of whether they are gay or straight. We are not changing religious marriage, or requiring religious groups to go against their traditions."

Margot James, the first openly lesbian Tory MP, said: "The Government isn't introducing a change that will mean churches have to marry same-sex couples if they did not want to.

"There are many gay people who are committed people of faith. They have a profound need to marry in a more traditional setting than would be provided by a civil partnership."

Another gay Tory MP said: "There are some on the traditional right who can't countenance the move, but I think you will find they are less of them than you might expect."

However, gay rights groups fear the legislation may not be included in the Queen's Speech. Ben Summerskill, chief executive of Stonewall, said: "It does seem bishops and ex-bishops should worry rather more about global poverty and the HIV pandemic than what might be going on in Shrewsbury register office."

Tory supporters of the anti-gay marriage campaign include David Burrowes, the MP for Enfield Southgate, Fiona Bruce, the MP for Congleton, and Edward Leigh, the president of the right-wing Cornerstone Group.

Mr Burrowes said he had received a "barrage of hostile, hate-filled emails and tweets", including a death threat, after The Independent revealed he would lead the Commons campaign against the planned legislation.

Lance Corporal James Wharton, 25, a Household Cavalry soldier who entered a civil partnership with his boyfriend two years ago with the blessing of the regiment, said: "This is the same old faces, who oppose anything to do with gay issues in this country and always kick up a fuss."

The comedian Julian Clary said: "Lord Carey's comments are very predictable. All these comments seems to come out of fear. In 10 years, when gay marriage is normal, we'll have forgotten all about this. He should have one of his pills and shut up."

Case Studies

"Civil partnership doesn't reflect the fullness of our relationship"

Sharon Ferguson

53, London

A senior pastor at the Metropolitan Community Church in London, Sharon and her partner Franka Strietzel, 50, see marriage as a more appropriate way to celebrate their relationship.

"We have wanted a marriage, rather than a civil partnership, for a long time. The reason for that is that I am an ordained rector. I believe in the civil partnership, but it's a legal agreement. Civil partnership very clearly does not require any sexual element. It doesn't reflect the fullness of our relationship. I want to be able to have a covenantal agreement between me, my partner and God. When you make a commitment in a marriage, people know that it is permanent and long-term. When you introduce someone as your partner, they ask: 'Your business partner?' "

"It feels like the romance is being taken out of our big day"

Jennifer Krase, 25, Bangor

Jennifer is an American student at Bangor University in Wales. She is due to enter a civil partnership with her English fiancée Georgia Mannion in July.

"The whole attitude of the state towards civil partnerships seems to be that this is not the same as getting married, that it is more like a promise between friends. That is disappointing because it feels like the romance is being taken out of our big day. I do want to marry my partner for the advantages it gives. But that does not change the fact that I want to marry my partner because I love her."

"I'd love my family to come to the wedding ceremony"

Glenn Kerr Arbesú, 46, Glasgow

Glenn is a translator who entered a civil partnership with Mexican Gabriel Kerr Arbesú in 2009. He said he had to explain to his son why he and his partner could not call themselves a married couple.

"I had to explain that the law defines marriage as about producing children. I felt having to explain that to my son diminished our relationship. He's a clever boy and I'm glad that he asked, but it was hard.

"I would like to call myself married. I have a big family - seven brothers and a sister - and I would love, when I get married, for them to come to the ceremony. Just like anyone else, I want my children to be in my wedding.

"Same-sex marriages are now legal in Gabriel's hometown of Mexico City, but we have decided to wait for British laws to change."

"The same old faces oppose anything to do with gay issues in this country"

Lance Corporal James Wharton, 25, Windsor

L/Cpl Wharton is a Household Cavalry soldier who entered into a civil partnership with Thom McCaffrey two years ago with the blessing of the ancient and distinguished regiment. He said: "I think it [gay marriage] should be brought in. It is the right thing to do.

"When the Civil Partnership Act was introduced, everybody opposed it. Now they are saying civil partnerships are all right and oppose gay marriages. They change their minds to suit themselves.

"This is just the same old faces, who oppose anything to do with gay issues in this country and always kick up a fuss. It is ridiculous."