Britain's Jason Kenny has been promoted to world individual sprint champion after Frenchman Gregory Bauge was suspended for drug test infringements.
Bauge has been stripped of the title he won in Apeldoorn in March by world governing body the UCI.
Sir Chris Hoy moves up from bronze to silver as a result of the suspension.
In the team sprint, Germany are promoted from silver to gold, Britain from bronze to silver, and Australia from fourth to bronze.
It is a first world gold for Kenny, who won the team sprint title at the Beijing Olympics in 2008.
"The news came as quite a surprise and whilst it's an honour to get my first senior World Championship title, I would have preferred to have achieved it under different circumstances," said Kenny.
"I am looking forward to riding the rest of the season wearing the rainbow jersey."
The UCI took action after Bauge received a backdated suspension from the French federation.
France also lose the team sprint world title as Bauge took part in the races.
- Born 31 January 1985 and a member of the French senior track cycling team since 2003
- Has won six world titles, not including two won in 2011 but annulled by governing body the UCI in January 2012
- Helped France win team sprint silver behind Britain at the Beijing Olympics
- Seen as one of the biggest threats to Britain in the men's sprint races at London 2012
The French cycling federation handed Bauge a 12-month suspension in response to one missed test in 18 months and a violation of rules governing rider availability for drug tests.
The suspension was backdated to 23 December 2010 and hence expired on 22 December 2011, but the UCI has now decided that all of Bauge's results in that period - including his two world title-winning races - will be annulled.
Kenny, 23, beat Hoy in the semi-final during last year's World Championships, but lost his subsequent clash with Bauge for individual sprint world gold.
"It's a shame to finish on a loss but I'm really pleased with a silver medal," Kenny said at the time.
The AFP news agency reported that Bauge's lawyer, Jim Michel-Gabriel, had questioned the impartiality of the UCI in the wake of the announcement.
"They are not blaming him [Bauge] for doping, they are blaming him for having overlooked his administrative obligations. And these are debatable, as one of them arose simply because he was ill," Michel-Gabriel was quoted as saying.
"There is no reason to strip him of his titles.
"The only direct rival to Mr Bauge was an Englishman and, as you are aware, the 2012 Olympic Games are being staged in London."
Bauge's backdated suspension means he is clear to compete at London 2012, having helped France to a silver medal behind Britain in the team sprint at the Beijing 2008 Olympics.
He is also likely to feature in February's Olympic test event at the Velodrome on the Olympic Park, which doubles as a stage of track cycling's World Cup and is set to feature both Hoy and Kenny among a strong British line-up.