The government is being urged to explain why Merseyside gyms are shut but Lancashire's are open despite both being in highest Covid alert level.
Liverpool City Region Mayor Steve Rotheram said he was "concerned" at the differences over gym openings.
Meanwhile, soft play centres and car boot sales are being closed in Lancashire but not in Merseyside.
A Department of Health and Social Care spokesman said "intensive discussions" had taken place with local leaders.
Lancashire has agreed to move into tier three from Saturday, joining Liverpool City Region in the top level of England Covid restrictions.
Southport MP Conservative Damien Moore called on Health Secretary Matt Hancock to immediately reopen "gyms in Southport and the wider-Merseyside region".
"We need fairness and parity in these restrictions," he said
Mr Moore also told the Local Democracy Reporting Service (LDRS) that Mr Rotheram "didn't fight hard enough for a better deal from the government and he failed to keep gyms open when leaders in Lancashire did".
But Mr Rotheram denied this in a joint statement from city region leaders, saying: "We were given no choice about the specific package of measures that would be applied to us, or the scientific evidence to support them.
"We therefore require Government to explain, with evidence, why they believe gyms in the Liverpool City Region are a greater risk for Covid transmission, than those elsewhere."
Gym owner Nick Whitcomb, who has already been fined £1,000 for keeping his business open, told BBC 5 Live he believed the decision to close gyms in the Liverpool City Region was an "oversight".
Mr Whitcomb added: "Once the decision making has been passed back to the local authorities I think we are going to follow Lancashire."
A DHSC spokesman said: "Soft play and car boot sales, which remain open in Merseyside, are closed in Lancashire, whereas the opposite is the case for gyms.
"Arcades, betting shops and casinos are closed in both areas."
He added other interventions were "subject to consultation with local authorities based on local evidence".