Sports events with an attendance of around 20,000 or more spectators may require proof of full vaccination, according to reports.
Plans being considered by the UK government would see the ruling come into place from the end of September.
In a press conference on Monday, Prime Minister Boris Johnson outlined plans to employ certification at nightclubs and "other venues where large crowds gather."
Chief scientific adviser Sir Patrick Vallance added that this was due to them being "potential super-spreading events" because of close-contact crowds.
This is a deviation from when the government allowed more than 60,000 to attend the semi-finals and final of Euro 2020 at Wembley earlier this month.
The matches were overseen by the Events Research Programme, in which a negative Covid-19 test or proof of full vaccination would allow you inside the stadium, among other strict regulations.
That shared similarities to how adults gained access to the British Grand Prix at Silverstone on Sunday, where the 140,000 crowd was the largest for a sporting event in the UK since the pandemic began.
Now, though, it appears that testing could be obsolete and vaccine passports will be king.
BBC Sport claim that the definition of what constitutes a large crowd and the potential venues are yet to be finalised.
The PM's official spokesperson stated: "We're not seeking to draw lines around particular settings.
"I think Professor [Jonathan] van Tam and the PM talked about the sort of areas where we'd be looking at enclosed spaces where large groups of people are brought together.
"We're going to be looking at the latest data which currently is very focused on nightclubs. But we'll be looking at the data both here and globally to consider what's the best approach."
A government spokesperson explained: "As the Prime Minister said, we reserve the right to do what is necessary to protect the public and reduce transmission, including mandating Covid certification in certain settings.
"We are working closely with organisations that operate large, crowded settings, where people are likely to be in close proximity to others outside their household, to encourage the use of the NHS Covid pass, where appropriate."
Should vaccine passports be implemented into watching sports with large crowds? Comment your opinion below.
The reports have led to confusion for sporting governing bodies both indoor and out, with The Racecourse Association saying dialogue would be needed between the government and relevant stakeholders "to understand the detail behind this plan," and described it as a "significant logistical operation."
The RCA went on to add: "It is vital that horse racing and the wider sports/leisure economies have contingency plans to avoid commercially damaging restrictions being re-imposed but equally allow us to host safe events."
Earlier this month, it was confirmed that spectators would not require proof of vaccination upon the lifting of restrictions on Monday, July 19, although some sports clubs have requested a negative test to attend.
English Football League Chief Executive, Trevor Birch, commented on the situation, affirming that EFL would "remain vigilant" in its preparations and "continue to engage" with its clubs and the authorities.
"We have long said that getting fans back into our stadia is an economic necessity for EFL clubs, that have lost millions over the past year and now need to be able to plan with clarity on and off the pitch," stressed Birch.
"Having experienced the highs of Euro 2020 following England all the way to the final this summer, supporters across the country will now be counting down the days until they can return to watch their beloved teams in person, and we know that clubs have been working very hard behind the scenes making plans to welcome supporters back safely."
