Thomas, who today launched the Tackle HIV campaign with ViiV Healthcare to improve public understanding of HIV and break the stigma around it, said: "I felt maybe nine months ago when I spoke about my HIV diagnosis that I started a conversation and it becomes relevant for a while, but then the conversation stops.

"What I wanted to do was to keep that conversation going because at the start of this campaign we did a survey and the results kind of shocked and scared me a little bit."

A recent Tackle HIV survey, conducted amongst 4,000 adults in the UK, highlighted the stigma and misunderstanding still attached despite advances in science and medicine.

Of those surveyed, 81 per cent said the main reason why they would or might end a relationship with a potential partner who was HIV positive was being worried about contracting HIV themselves.

Fewer than one in five people know that if a person living with HIV is taking effective treatment, they cannot pass it on while 34 per cent said they would not play contact sport if they knew one of their opponents had HIV.

Thomas added: "I live a full and happy, normal, healthy life taking one single tablet a day which means I'm undetectable so I can't transfer HIV onto another single person whether it be on a rugby field or any other environment."

When the ex-British and Irish Lions captain revealed he had been diagnosed in September, the Duke of Sussex was one of many to offer their support.

A minority were not so positive and Thomas, who came out as gay in 2009, confirmed he had been subjected to abuse on social media.

"It is not really about me. It's about people who are being stigmatised against and who are living with discrimination and the reality is this is something they shouldn't be discriminated by," he added.

"I feel really blessed. I have had really strong, positive support face-to-face. I have had discrimination on social media, but sadly – and it sounds weird and I shouldn't even say this – that is the norm for social media anyway.

"What that does give me is a reality that maybe I am living in this environment now where people are supporting me because people feel like they have been affected by HIV so they've learnt about HIV, learnt I am no risk to them and learnt I live a happy and healthy life."

Sir Elton John, David Furnish and the Terrence Higgins Trust are supporting this Tackle HIV campaign, which will work to change negative perceptions and make HIV better understood and accepted by the general public.

Thomas said: "I was the self-version of stigma. When I found out, I thought I was going to die.

"My first thought process was how long do I have left to live and do I have enough time to tell my family and friends that I am dying of a virus.

"It took me a long while to find the education to be OK and to have the knowledge to live with it.

"I am not shouting at people saying they should know better because 20 or so years ago the government released a pretty strong, scary advert telling people HIV – or Aids as it was referred to then – was a killer.

"People feel like nothing has been done since to re-educate people. People think they already know what happens when you live with it."

Tackle HIV, a new campaign led by Gareth Thomas in partnership with ViiV Healthcare and the Terrence Higgins Trust, aims to tackle the stigma and misunderstanding around HIV. For more information visit www.tacklehiv.org and follow @tacklehiv