The High Court decision to deny heterosexual couple Rebecca Steinfeld and Charles Keidan from entering a civil partnership has been described as a "defeat for love and equality".
Steinfeld and Keidan, who are academics, used the words of a human rights activist to sum up their feeling after the denial, adding that they were "deeply disappointed" in the decision.
During the fight an online petition in favour of expanding civil partnerships to opposite-sex couples gathered more than 36,000 signatures.
Using the Change.org website they posted an update after the ruling with a comment from LGBT Human rights campaigner Peter Tatchell, who described it as a "huge disappointment".
"This is a defeat for love and equality. It will be a huge disappointment to the thousands of heterosexual couples who would like to have a civil partnership. The court has rejected the principle that in a democratic society everyone should be equal before the law. It says that opposite-sex couples are not entitled to the same choices as same-sex ones.
"It cannot be right that same-sex couples have two options, civil partnerships and civil marriages; whereas opposite-sex partners have only one option, marriage. This legal case was always about the simple quest to end discrimination and ensure equality for all. I hope Charles and Rebecca will appeal and that justice will prevail in the end," he said.
Steinfield and Keidan themselves wrote a lengthy response to their supporters, which read: "We’re deeply disappointed to share with you the news that our Judicial Review claim has not been successful. We know that you will share our disappointment.
"The Judge ruled against us because she decided that our case did not fall within the ambit of Article 8 of the European Convention on Human Rights, a right to respect for one’s private and family life. The Judge also ruled that the Government is entitled to take its time to decide on the future of civil partnerships in order to avoid costs resulting from changing legislation too soon.
"The Judge did however acknowledge that there will be many people who sympathise with our view “that it is unfair that a route to state recognition of their relationship which is open to a same-sex couple…remains unavailable to them because they are heterosexual.” But this did not prove, in her judgement, to be sufficient grounds for a ruling in our favour," it read.
Both partners describe themselves as feminists and said they had challenged the legal ban on heterosexual couples entering into civil partnerships as they reject marriage as a “patriarchal” institution.
An online fundraiser also raised more than £22,000 towards their legal costs.
A family lawyer commenting on the case, Lauren Evans, Kingsley Napley LLP, told the Huffington Post UK:
"This is a surprising decision and crowd funding for an appeal starts today. The law at the moment clearly discriminates on the grounds of sexuality. Everyone, be they straight, gay or bisexual, should have the same freedom to choose how to define their relationship.
"Parliament needs to step in to correct this hangover from a Government that was unwilling to go all the way first time around with the Civil Partnership Act. Today, by coincidence or fate, the Private Member’s Bill designed to correct this inequality has its second reading in the House of Commons.
"It has cross-party support from MPs, as well as support from lawyers, academics and a petition with over 36,000 signatures. Steinfeld and Keidan’s case has turned up the volume of this campaign. Hopefully, regardless of today's judgment, Parliament will now open its ears and eradicate this discrimination forever.”
Before the High Court challenge, Steinfeld, 34, said: "We are taking this case because the UK Government is barring us, and many thousands of opposite-sex couples like us, from the choice of forming a civil partnership, and we want this to change.
"Personally, we wish to form a civil partnership because that captures the essence of our relationship and values."
She added: "Civil partnerships are a symmetrical, modern social institution conferring almost identical legal rights and responsibilities as marriage, but without its historical baggage, gendered provisions and social expectations.
"We don't think there is any justification for stopping us or other opposite-sex couples from forming civil partnerships."
Keidan, 39, said: "We believe that opening civil partnerships to opposite-sex couples would complete the circle of full relationship equality that began with the hard-won victory for same-sex marriage.
"We campaigned for equal marriage and believe that the significance and symbolism of opening marriage to same-sex couples cannot be overstated."