The Conservative candidate in the West Midlands metro mayor race has defended spending up to £1m on campaigning.
Andy Street said he "had not spent quite £1m" as reports suggested but accepted he had "spent a substantial amount more than my opponents".
The ex-John Lewis boss said the cost was "absolutely appropriate" and the 4 May election was "a new start in democracy" for the region.
Other candidates said it was unfair and called for the rules to be tightened.
Spending in the final weeks of campaigning is capped at £130,000, but there is no limit before then.
On Thursday, six people will bid to become the region's first metro mayor, taking on powers over economic development, education and skills, housing and transport.
All six raised £5,000 to be included in a West Midlands Combined Authority booklet.
Mr Street said: "Everyone has the same rules to work within, we were able to raise that money."
The candidate was asked by BBC Radio 4's Today programme about being referred to as the "Donald Trump of British politics".
He replied: "Everyone loves that line. There's one similarity of course, a business background... but there the similarity ends in terms of our beliefs."
Labour's candidate Sion Simon told Today the regulated period begins much earlier for general elections.
He added: "You can't blame Andy for sticking to the rules but it does beg the question whether the rules are right.
"No rules at all, a complete free-for-all, until six weeks before polling day - I don't think that's the right way to go about this.
Labour's campaign, which was partly focused on social media campaigning, has cost up to £200,000.
"We've spent nowhere near - not even in the region of - what the Tories have spent," a campaign spokesman said.
Beverley Nielsen, the Liberal Democrat candidate, said she had raised about £50,000 for campaigning and could not afford to leaflet every house.
She said mayoral elections should have the same funding regulations as other elections, adding: "The public should hear the voice of all parties."
UKIP's Pete Durnell said a spending cap was needed to give "small parties a chance".
"Aside from the booklet, my campaign would have cost £3,000. It is not a level playing field - we are not even on the same field."
Graham Stevenson, the Communist candidate, said his total cost was about £12,000.
The Green Party's James Burn, who raised nearly £6,000 for the campaign through a crowdfunding website, expects the party will spend £15,000 to £20,000 in total.