Oleg Tinkov, the Russian multimillionaire owner of the Tinkoff-Saxo team, has challenged the four best riders in the world to contest all three Grand Tours in 2015 for €1 million.

The eccentric Russian would like to see Alberto Contador, who rides for his Tinkoff-Saxo squad, Team Sky's Chris Froome, Astana's Vincenzo Nibali and Nairo Quintana of Movistar race in the Giro d'Italia, Tour de France and Vuelta a Espana in the same year.

The €1m purse could be divided equally, or be awarded as a prize to the rider who places best at the Tours of Italy, France and Spain.

Many cycling fans are relishing the 2015 Tour de France, where the quartet are expected to meet to contest for the yellow jersey won by Nibali in 2014.

The route of the Giro d’Italia, announced earlier this week, suggested a Giro-Tour double might be possible, but few riders ride three Grand Tours in a calendar year, let alone contest for the overall victory at them.

Tinkov called for his gruelling challenge to be adopted in an interview with Italian newspaper Gazzetta dello Sport and then took to Twitter to 'call out' Contador's rivals publicly, including addressing Team Sky principal Dave Brailsford.

Tinkov wrote: “ davebrailsford chrisfroome vincenzonibali NairoQuintana dont be a chiken (sic)! #Real3GTchallenge”

Jonathan Vaughters, head of the Garmin-Sharp team, suggested Tinkov's plan was good for cycling.

“In every successful sport, the best athletes compete against each other, all year, in the biggest (same) events. So, yes, I agree,” Vaughters wrote on Twitter.

However, there will be concerns a sport which has endeavoured to tackle the use of performance-enhancing drugs will be leaving itself susceptible to abuse if such a gruelling challenge is contemplated.