Fifa will reveal who will stage the 2018 and 2022 World Cups on 2 December
Football's world governing body Fifa has widened its probe into the bidding for the 2018 and 2022 World Cups.
Proceedings have already been opened against two executive committee members as part of an inquiry into allegations they offered to sell their votes.
And investigations are also ongoing in relation to other Fifa officials who may have been involved.
But Fifa will also study any "alleged agreements between member associations" bidding for the 2018 and 2022 events.
It did not specify which countries could be under scrutiny.
Rumours of collusion between a 2018 bidder and a 2022 hopeful surfaced in September, prompting Fifa secretary general Jerome Valcke to warn all countries that mutual voting deals are against Fifa rules.
England, Russia, Spain/Portugal and Netherlands/Belgium are competing to stage the 2018 World Cup, while the United States, Australia, Qatar, Japan and South Korea are all in the hunt for 2022.
Transparency and fair play are not words that immediately come to mind when you look at the bidding process
Alec McGiven, England's 2006 World Cup bid director
Alec McGiven, the director of England's unsuccessful bid to host the competition in 2006, described the latest revelations as "tremendously damaging".
"Fifa's World Cup is the biggest football competition in the world, it's tremendously important to football fans," he said. "They want to see it run properly and they want to see the bidding process to be a fair one.
"Sadly, transparency and fair play are not words that immediately come to mind when you look at the bidding process."
Fifa is concerned that any agreement between member associations would be a "clear violation of the bid registration document".
"An investigation has also been opened into the member associations in question as well as their bid committees," read a Fifa statement issued on Monday.
"Fifa has again asked the chairman of the ethics committee to act without delay to take all possible steps, including the possibility of provisional measures, should the relevant conditions be met."
Monday's development follows an English newspaper accusation that Nigerian Amos Adamu and Tahitian Reynald Temarii, who is the Oceania Football Confederation (OFC) president, allegedly asked for payments for votes.
Amos Adamu is one Fifa member named by the Sunday Times
Adamu and Temarii were secretly filmed by reporters from the Sunday Times, who posed as lobbyists for a consortium of American companies that wanted to bring the tournament to the US.
Adamu allegedly said he wanted $800,000 (£500,000) to build four artificial football pitches. This would be against Fifa's rules.
Temarii is also alleged to have asked for a payment, in his case to finance a sports academy.
The OFC said it is investigating the reports.
"Further to information made public by the Sunday Times, the OFC president and Fifa vice-president Reynald Temarii will cooperate fully with the Fifa Ethics Committee and the Fifa secretary general," a statement released on Sunday read.
"Reynald Temarii welcomes a full and thorough investigation so that all the facts can be heard."
Fifa president Sepp Blatter said at the weekend that the affair had had a "very negative impact" on football's world governing body.
"The Sunday Times allegations could not have been more stark and more uncomfortable," said BBC sports news correspondent Tim Franks.
Franks added that the regulations governing the World Cup bidding process are not as rigorous as they could be.
"The competition among countries is lengthy, complex and - so far - not governed by the sort of strict rules that for the last decade have surrounded the bids to stage the Olympic Games," he added.
"Earlier this month, a very senior official at Fifa told the BBC he had concerns that England's competitors to stage the 2018 World Cup were not playing as straight as England... and that several members of the executive committee might be open to blandishments."
The England 2018 team hope there will be no backlash against their bid from Fifa members angry that an English newspaper had been investigating them undercover.
England had targeted Adamu as one of the crucial 'neutral votes' they needed to win the World Cup bidding contest.
Bid officials arranged for David Beckham to meet the Nigerian in Cape Town in November last year.
Former Manchester United striker Andy Cole and ex-bid chairman Lord Triesman then flew to Nigeria the following month to make a formal presentation to Adamu, a Red Devils supporter.
Adamu's vote was seen as vital in that he was one of four Africa Fifa members and no African nations can bid for either 2018 and 2022.
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