Although the commission's findings will not guarantee a winner, a critical report on any of the five hopefuls -- Madrid, Paris, London, Moscow and New York -- will almost certainly prove fatal.

The commission, led by 1984 Olympic women's 400m hurdle champion Nawal El Montawakel, began its study on Wednesday when the 12-strong team touched down in Madrid.

For the next seven weeks all five would-be hosts will be visited and then the commission will publish its findings in May.

The 2012 report will carry more weight than in previous bids.

Even since the Salt Lake City scandal in 1999, when 10 IOC members were either expelled or resigned, members have been banned from visiting bid cities.

The IOC ethics commission has also introduced draconian restrictions on the bid cities, dramatically reducing their chances of meeting IOC members and trying to win over their vote.

Even a planned debate between the five cities to be shown on BBC World was rejected by the ethics commission.

Members of the evaluation commission have been barred from talking to the press during their whirlwind trips to the five cities.

"We had to sign a confidentiality agreement," members of the commission have told AFP.

The visits by the commission will be a nerve-wracking time for the cities. Their plans to host the Games will come under the microscope and the slighest hiccup could dash their hopes.

The final report will not list the cities in order but IOC members know how to read the carefully crafted observations in the conclusion where key phrases make it clear the commission's verdict.

Both London and Madrid will be using their Royal families to try and impress the evaluation team at an official reception.

All five cities will also be hoping to ensure there are no public protests by people opposed to the Olympics coming to the city.

IOC members are very wary of protest groups, they need to know that they are welcome.

On the eve of the start of the tour, Paris is considered favourite to win in Singapore, with New York and London close behind. Madrid and Moscow are considered as outsiders.

But the battle to win 2012 is expected to be the closest in modern history, with the winner being announced at the IOC Congress on July 6 in Singapore.

A bad evaluation report or a host of other politcal machinations within the IOC can derail a bid.

Originally the 2012 vote was to be the star item at Singapore but it has now been overshadowed by the expected move to expell IOC members Ivan Slakov and vice-president Kim Un Yong for bringing the movement into disgrace.

Slavkov was caught on a BBC Panorama sting into vote buying within the IOC. Kim was jailed for two years by a Korean court on corruption charges.

Both men are expected to fight the bid to oust them and members' minds are more likely to be fully focused on the fate of Kim and Slavkov than the fate of the 2012 candidates.

FACTBOX
A factfile on the five 2012 bid cities -- London, Paris, New York, Madrid and Moscow - and where they stand five months from the vote in Singapore on July 6.

LONDON
Population: City -- 2.9 million, Greater London -- 7.4 million

Bid slogan: "Back the bid"

Cash investment: 3.8 billion dollars for the Games, 15.8 billion on infrastructure.

Main Olympic stadium: 80,000 capacity for Games, reduced to 25,000 for use after the Games.

Distances: 97 per cent of athletes will be within 30 minutes of their venue, 80 per cent within 20 mins.

Previous Olympics: 1908, 1948

Chances: London got off to a bad start but have made up ground fast with bid leaders Seb Coe and Keith Mills making their presence felt. Considered by some observers to be second to Paris at this stage, London will need a massive final push to pull off victory.

MOSCOW
Population: 10.5 million

Bid slogan: "Believe in one's dream"

Cash investment: 8 billion dollars for Games and infrastructure

Main Olympic stadium: 80,000 capacity.

Distances: the majority of Olympic venues will be situated within 12km distance from the centre of the city. The maximum distance between the venues will be approximately 22-25km.

Previous Olympics: 1980

Chances: Moscow were lucky to make it to final five and only intense political pressure got them through. Bid driven by Moscow Mayor and so far failing to win many converts. Cannot be ruled out but have a lot of ground to make up on their four rivals.

PARIS
Population: City -- 2.3 million, Greater Paris -- 11.2 million

Bid slogan: "L'Amour des Jeux" (Love of the Games)

Cash investment: 2.6 billion dollars for Games, 6.2 billion dollars for infrastructures.

Main Olympic stadium: 80,000 capacity (Stade de France)

Distances: 75 per cent of events will take place within 12kms of Olympic Village.

Previous Olympics: 1924

Chances: Began campaign as favourites and still considered the front runners which is not necessarily a good thing this far out. Quietly working in the background to win votes and doing everything not to make a major mistake. New team has learnt from failure of the 2008 bid.

NEW YORK
Population: 8 million

Bid slogan: "Let the dreams begin"

Cash investment: 7.5 billion dollars for Games and infrastructure

Main Olympic stadium: 78,000 capacity

Distances: No Olympic site will be more than 30km from Village.

Previous Olympics: None

Chances: Are fast making ground on pre-vote favourites Paris. Claims that US foreign policy will kill off bid are grossly exaggerated. Much depends on bid leader Dan Doctoroff, who has been confirmed as head of New York Organising Committee if bid successful. If IOC members like him, much needed votes could be secured.

MADRID
Population: 3.1 million

Bid slogan: "Preparados para ti" (Ready for You)

Cash investment: 6.47 billion euros

Main Olympic stadium: 75,000

Distances: Most events will take place in a 10km radius

Previous Olympics: None

Chances: Trailing Paris and London at present. Several people close to bid admit their chances are slim. Hampered by fact that 1992 Games were held in Barcelona. Reports that former IOC president Juan Antionio Samaranch is less than impressed with top Madrid bid officials.