Sheffield City Region mayor Dan Jarvis, who was elected in 2018, describes himself as "the only Labour mayor in government" because of his dual role as MP for Barnsley Central.
In an interview with Big Issue North, he said his access to Ministers at Westminster as a Labour MP "means that I see the limitations of devolution under the existing model".
And he said: "I spend too long tinkering as a mayor, when I could be transforming. The reality is it’s only as an MP that you have access to Treasury to deliver transformation.”
But asked whether this meant his days as mayor were numbered, he told Northumbria University academic Katy Shaw: “I have to make a choice, because it isn’t sustainable to keep doing both these roles for the long term. I have to make my mind up soon – and I will.”
Mr Jarvis, who was elected in Barnsley Central in 2011, sparked debate when he stood as a mayoral candidate while serving as a Labour MP.
Before he was elected mayor in 2018, the party's National Executive Committee (NEC) ruled that no-one could serve in two elected roles.
He was later backed by the Yorkshire and Humber Parliamentary Labour Group to be allowed to do both jobs, with NEC's stance described as "unfair" and "undemocratic".
He initially received no pay for his mayoral work as the South Yorkshire devolution deal agreed last year was incomplete.
But following its implementation, an independent panel suggested Mr Jarvis should be paid £79,500 a year in addition to his Parliamentary salary. Mr Jarvis said this would go to local good causes.
His counterpart in the Liverpool City Region, Steve Rotheram, quit as an MP when he took on the metro mayor role. And Labour's candidate to be West Yorkshire mayor, Tracy Brabin, says she will stand down as Batley & Spen MP if she wins.
Last month, Mr Jarvis told The Yorkshire Post's political podcast Pod's Own Country that "the world feels a very different place to me from when I first decided to run as as the South Yorkshire mayor".
He said: "Since then we've seen Britain's departure from the European Union, we've seen obviously the massive impact that Covid has had, we've seen the developing devolution story around the country.
"So I do really believe in the power of mayors to do good and to make a difference and it is a wonderful privilege to serve in this role. Ultimately, what I will have to do is, is take a view about what's in the best interests of my constituents and decide what I'm going to do. over the longer term.
"We're not at that point, because all of my time every single day, seven days a week, without fail is consumed by responding to the huge pressures and the challenges of this pandemic.
"So hopefully, as we kind of come out the lockdown at some point in the not too distant future, there will be a moment of calm and I can sort of take a moment to assess where we've got to and think about the longer term future, but I do feel deeply privileged to be doing this mayoral role in the way that I do.
"I know it was a controversial decision that I took to remain in Parliament, it was the right thing to do, we wouldn't have got the deal agreed in South Yorkshire if I hadn't done that.
"So I'm lucky to do the two, I continue to feel very privileged to have the opportunity to do them both. And I will keep doing them for the duration of this term and then and then take a decision about what the future might hold."