Over 40 percent of the world's professional footballers have experienced delayed payment of wages, according to a wide-ranging survey published by global players' union FIFPro on Tuesday.

In the survey, carried out by the University of Manchester, 41 percent of the 13,876 players who responded had been forced to wait for their salaries over the past two seasons.

"It's a wake-up call for clubs and governing bodies," FIFPro General-Secretary Theo van Seggelen told reporters during a recent briefing in London. "We cannot accept it any longer."

The FIFPro Global Employment Report 2016 also found nine percent of players had suffered from violence and seven percent had been been approached to fix matches.

FIFPro hopes the survey, which is the biggest of its kind, will shed light on the problems faced by players playing outside glamorous championships such as England's Premier League or Spain's LaLiga.

The median net monthly income of players surveyed was $1,000 to $2,000, with 60 percent of respondents earning under $2,000 per month.

FIFPro has used the example of Nigeria international Michael Uchebo, who has not been paid by Portuguese top-flight club Boavista since April, to illustrate its findings on late payments.

The 26-year-old striker has been prevented from playing since the end of last season and, according to FIFPro, risks eviction from his house.

He has been banned from first-team training and has posted footage on social media that appears to show him being forcibly removed from Boavista's gymnasium and threated with violence by security staff.

"I don't understand why Boavista treat me like this," Uchebo said during a press conference in Lisbon organised by the Portuguese players' union.

"I asked them if I did something wrong. They are treating me like a slave."

Boavista did not wish to comment on the matter when contacted by AFP, but in a video posted on Facebook earlier this month, club president Alvaro Braga said Uchebo's statements "do not correspond to the truth".

Braga said Uchebo turned down opportunities to join other clubs during the close-season transfer window and had rejected a settlement -- which FIFPro says was one month's salary -- to terminate his contract.

- Scotland's violence threat -

World governing body FIFA's rules on overdue payments allow clubs to be 90 days late and the survey found 78 percent of players experiencing salary delays were paid within that timescale.

FIFPro wants the non-payment buffer to be reduced to 30 days, in the short term, and ultimately abolished.

"Not every football player has three cars in three different colours," said Van Seggelen.

"Our players are normal human beings and they deserve to be paid on time. Because they also have children and a mortgage."

The survey found there is an 11 percent chance a player will have been approached to fix a match by the time he passes the age of 33.

Players on relatively low salaries were found to be twice or three times more likely to be targeted by match fixers.

Nearly one in 10 players reported experiencing physical violence, with almost 16 percent reporting threats of violence.

Of those who said they had been victims of violence, 51 percent had been attacked by fans, 25 percent by fellow players and 12 percent by club officials or coaches.

Democratic Republic of Congo was the worst country for both violence and threats of violence from supporters on match days.

Scotland was surprisingly in second place in the latter category, with Brazil fifth and Italy sixth.

For threats of violence on non-match days, Italy was by far the worst country, with 24 percent of players saying they had been menaced by fans.

Fifteen percent of players said they had been victims of bullying or harassment, while 7.5 percent alleged discrimination based on ethnicity, sexuality or religious beliefs.

The survey contained no data from players in England, Spain, Germany, Portugal, the Netherlands, Argentina or Mexico due to non-existent or insufficient feedback.

Source: AFP