Olympic champion Adam Peaty has warned the government's decision not to reopen swimming pools could affect people's mental and physical health.
On Tuesday Prime Minister Boris Johnson said pubs were among the venues that could reopen on 4 July, but indoor sports facilities were not mentioned.
Peaty said the announcement was "disappointing, frustrating" and "doesn't make any sense".
Indoor facilities have been closed since March amid the Covid-19 pandemic.
Representatives of several sports are angry at being overlooked in the next round of lockdown easing measures.
Research in 2019 revealed that swimming saves the NHS around £357m per year by improving the health and wellbeing of the nation, something Peaty feels has been overlooked.
The government hopes indoor gyms, swimming pools and spas - so called 'close proximity' venues - can reopen in England later in July.
BBC health correspondent Nick Triggle reports that there is government concern that Covid-19 transmission will be more difficult to control in these venues because of the physical exertion by gym-goers, the damp conditions in changing rooms and the fact that social distancing is generally less easy.
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Peaty told BBC Sport: "People will talk about how much the pubs bring in [to the economy] in terms of tax, but you also have to think about the health benefits that swimming provides.
"With mental health concerns on the increase we're in a dangerous position and there's a risk that if the pubs are open but they can't exercise then people will choose the pub each day and have no balance."
Peaty, the 50m and 100m breaststroke world record holder, also wants government support to help participation when venues open.
"Some venues struggle to make money and are at risk of permanent closure," said Peaty. "Then you have kids who haven't swum now in 15-16 weeks who may turn to other sports.
"If we're not careful we'll see a downturn in participation just before the Tokyo Olympics which is extremely wrong."
Peaty is among a small group of elite British swimmers who have been allowed to return to pool-based training in the past couple of weeks as they begin preparations for next year's rescheduled Games.
"We have our temperature checked on arrival, we wear masks, I'm swimming in my own lane," he said.
"If you use those simple mechanics [in leisure centres] I can't see any reason why they're still closed."
On Tuesday, Swim England launched the #OpenOurPools campaign demanding answers from the government. The petition has already secured over 30,000 signatures - including those of Peaty and double Olympic champion Rebecca Adlington.