It is a pursuit that – behind the glitz, sequins and sashays – is known for fierce rivalries and cut-throat determination. But the strain behind the smiles in the world of ballroom dancing is beginning to show, as its governing body pushes to ban same-sex couples from ballroom dance competitions, provoking outrage among competitors.

The British Dance Council is to consider proposals that would define a dance partnership as having to consist between a man and "a lady" on 21 July, just before a major competition in Bournemouth. If it is passed, it will ban same-sex couples from mainstream contests, regulating them to same-sex-only categories.

A change in the rules would see John Church and his partner Alex Lewall unable to defend their UK Closed Championship, over-35 pre-championship category title at the next championships at the end of the month. The pair are also currently ahead of 135 mixed-gender couples at the top of the national league in their over-35 pre-championship category.

"It's a totally regressive step and as far as we are concerned it would be the end of our dancing careers," said Church, who has been dancing with Lewalle for the past four years. "We don't want to be trailblazers, we aren't asking for special treatment, we just want to dance and to be judged solely on our dancing – not what sex we are." The pair, who are both gay but not in a relationship with each other, are a striking partnership, standing at 6'4" and 6'2" respectively in their traditional tails and bow tie.

"The first time people see us dance, it does look a bit strange, but soon we are judged for our dancing, not our gender," said Church. "We have had so much support from other dancers, organisers, judges – when Alex and I won our category last year we were given a standing ovation. I think this objection is coming from a minority, but sadly they do get heard."

Same-sex dancing couples would be banned if a change to the rules – which has been proposed by the BDC rules committee – is approved by the board of directors on 21 July. The rules would, if passed, state: "This council recognises a partnership to be one man and one lady in all adult amateur and professional competitions and championships unless otherwise stated." The British Dance Council's president, Bryan Allen, said in a letter to members that the rules should "take into consideration the feelings of the competitors, the physical strength and stamina of a same-sex couple who might be included in a competition".

He told the Guardian that the BDC had received "many more letters of support for the change than against". The change in the rules was not discriminatory and would not result in a ban on same-sex couples, he said, but mean there would be a category which was only open to mixed couples. "People are disgruntled because they say while there is a same-sex-only category there is no mixed-only category – and I can see a basis in that claim," he said. "They can also claim that two men are physically stronger: for example, you wouldn't have two men playing in the mixed doubles at Wimbledon."

But the rationale was dismissed by Church. "Dancing isn't about power, it's about technique, positioning, poise, presentation – physical strength doesn't come into it," he said.

Same-sex competitors argue that there are not enough couples to make all-male categories competitive, while the most competitive mainstream categories would, if the rules were changed, only be open to mixed-sex couples.

It is currently not specified that partners in competitions must come from opposite sexes, and two women dancing together has long been a commonly accepted practice. The best known same-sex pair on the ballroom dancing scene are perhaps Bradley and Soren Stauffer-Kruse, the married gay couple better known as the Sugar Dandies, who were semi-finalists on Britain's Got Talent in 2012.

Although there are only a handful of same-sex couples competing, the number is increasing, said the human rights campaigner Peter Tatchell, who is supporting the campaign against the rule change.

"It is hard to know for certain what is going on behind this rule change, but is does seem to be linked to the growing number of same-sex competitors and their increasing success," he said, adding that a same-sex dancing ban might be illegal under the Equality Act 2010.

"We are concerned this proposed ban may be motivated by some judges, competitors and spectators not being comfortable with the participation of same-sex dance partners."

Heather Devine is also due to compete with her female dance partner Chrisi Lyons in Bournemouth. The pair are the current European same-sex senior women's champions. "It's awful and very upsetting," said Devine, who takes the lead in the pair's dancing and wears an embellished female-cut suit. "We have been practising almost every day, we have invested a lot of time and money, and if they change the rules it will all be for nothing."

But she also fears that it could have a damaging impact on the future of dancing. "It seems strange when the rest of society is becoming more accepting," she said. "The younger generation is far more open and individual, but I worry dancing could be going the other way."