The sun shone for Manchester City as the Premier League champions celebrated their long-awaited and dramatic title win with a euphoric victory parade but the event was marred when Tevez held up the controversial banner.
The Argentine striker was caught on camera holding up a mock tombstone banner with the words 'R.I.P. Fergie' in reference to Manchester United manager Sir Alex Ferguson.
"The creation of the tasteless material is in itself reprehensible. In accepting and brandishing it, Carlos has made a significant error of judgement," said a City spokesperson.
"The club wishes to express its sincerest apologies to Sir Alex Ferguson and Manchester United for any offence or distress caused."
United accepted the apology, with chief executive David Gill telling Sky Sports News: "I think it's right. The club acted pretty quickly. I think it was rather silly, frankly, in terms of what it said, but City acted with commendable speed. We move on and concentrate on other issues."
Tevez later added: "I got carried away in the excitement of the moment and I certainly didn't mean any disrespect to Sir Alex Ferguson, who I admire as a man and a manager."
Tevez, who played under Ferguson at United, has courted controversy all season.
It came at the end of a campaign in which Tevez spent more than three months in Argentina on unauthorised leave during an extraordinary dispute with the club.
Tevez returned to City to play an influential role in their title run-in but continued to divide opinion among fans despite making peace with manager Roberto Mancini.
It was widely assumed he would still look to leave the club when he returned from his self-imposed exile in February and apologised for his conduct, but he has recently said he wants to stay.
It is unclear where he obtained the banner but he did not appear to have it when he boarded the bus to begin the tour of the centre at Albert Square.
The meaning behind it could well be in reference to Ferguson's response to a 2009 question as to whether or not United would ever be underdogs against City. "Not in my lifetime," the Scot said.
Little could dampen the mood of City fans though as they celebrated their dramatic title victory on the streets of Manchester.
Twelve months ago Manchester United's players needed umbrellas after it rained on their celebrations following a record 19th English championship.
But under clear skies, 24 hours after an extraordinary 3-2 victory over Queens Park Rangers secured their first title for 44 years, Manchester's streets were transformed into a sea of blue as up to 100,000 City supporters lined the pavements.
Many fans on the two-mile route were too young to recall City's last title triumph in 1967-68 when they finished two points clear of United.
Others, with their team trailing QPR 2-1 in stoppage time, had poured out of the Etihad Stadium believing Roberto Mancini's side had blown the title before late goals by Edin Dzeko and Sergio Aguero snatched it from United's grasp on goal difference.
"Yeah, a little," said Argentine forward Aguero when asked in front of fans whether he cried after scoring the title-clinching goal.
Over the years City have been mocked by United fans and this was their chance for payback.
As the United players drowned their sorrows two miles away at the club's annual player of the year awards night at Old Trafford, City players and fans partied on the streets.
Manager Mancini wore a blue and white City scarf as he waved to supporters, many with their faces painted in the club's colours, from the steps of Manchester town hall.
City's England goalkeeper Joe Hart addressed the fans.
"The place was shaking, I was shaking. It was one of the most dramatic days in my life," he said.
Graham Jackson, a 64-year-old City supporter, summed up the mood of euphoria.
"I thought I was going to my grave and never see them win it so I am so made up, I tell you," he said.
Another, Gary Aldridge, added: "I have never seen so many grown men cry, on the streets, it's just unbelievable,"
There were a couple of notable absentees from the parade in City's controversial Italian forward Mario Balotelli and influential midfielder Yaya Toure.
Balotelli had flown back to Italy following his international call-up for next month's European Championship.
He also missed the FA Cup parade last season, which marked the end of City's 35-year wait for a trophy, after being granted permission to return home.
Toure, a driving force in City's title charge, was in Monaco receiving treatment for an injury suffered against QPR.
But even their absence failed to spoil the party, certainly not for the man selling inflatable European Cups who did a roaring trade.
Next year City fans will hope their team is parading the real Champions League trophy through the streets of Manchester.