Fifa presidential candidate Prince Ali of Jordan says a co-operation agreement between the African and Asian football confederations is a "blatant attempt to engineer a bloc vote" in the election.
Prince Ali, 40, has asked the game's world governing body to investigate whether the pact breaks its rules.
The two confederations account for 100 of the 209 votes to be cast in the presidential election on 26 February.
Ali stood for the post in May but was defeated by incumbent Sepp Blatter.
Blatter, 79, was elected for a fifth term but then stood down and has since been banned for eight years.
What is the co-operation agreement?
The Confederation of African Football (Caf) has signed a Memorandum of Understanding with the Asian Football Confederation (AFC) to "strengthen, intensify co-operation and strengthen the capacity of various stakeholders in Africa and Asia" over the next four years.
The agreement was signed by AFC president Sheikh Salman bin Ebrahim al-Khalifa, who is standing against Prince Ali in the Fifa election, and Caf counterpart Issa Hayatou.
Why does Prince Ali object?
The president of the Jordanian Football Association believes the two confederations have agreed a deal to back Sheikh Salman, head of the Bahrain Football Association, in next month's election in Zurich.
Uefa general secretary Gianni Infantino, former Fifa official Jerome Champagne and South African businessman and politician Tokyo Sexwale are also standing.
"I have always promoted cross-regional understanding, however the timing of this Memorandum of Understanding looks like a blatant attempt to engineer a bloc vote," said Prince Ali in a statement.
"Questions must be asked: was this deal approved by the members of the executive committees of both the AFC and Caf and is the timing of the announcement, prior to a presidential election, acceptable?"
What happens next?
Domenico Scala, Fifa's audit and compliance committee chairman, is likely to decide whether the agreement breaches election rules.