AC Milan's Kevin-Prince Boateng walked-off the pitch in protest after being subjected to racist chants during a friendly match.
Manchester United's Rio Ferdinand stoked further controversy when he defied his manager to boycott wearing an anti racism t-shirt.
The FA must do more to tackle racism and other discrimination, MPs have said.
Northumbria Police confirmed they had received a complaint in the wake of City's 3-1 Barclays Premier League victory at Newcastle this afternoon.
It is understood 27-year-old Serbia international Kolarov became involved in a lengthy exchange with a supporter carrying an Albania flag as he warmed up on the sidelines during the game.
Swansea City confirmed one of their supporters has been arrested for allegedly making a racist gesture towards Norwich defender Sebastien Bassong during their 4-3 Barclays Premier League defeat at the Liberty Stadium.
The incident took place after Robert Snodgrass had scored Norwich's fourth goal from a free-kick in the 77th minute.
Bassong, who had scored earlier in the game, went to celebrate with his team-mates but quickly motioned to referee Howard Webb that he believed he had been the victim of a racist gesture
Police are investigating reports that a racist gesture was aimed at West Brom striker Romelu Lukaku by a fan at a Premier League match at Sunderland on Saturday.
Pictures appeared to show a man making monkey gestures at Lukaku, who is black.
The Northumbria Police force said it is "carrying out inquiries after a report of racist abuse was received at the Sunderland vs. West Brom match on Saturday."
A Metropolitan Police spokesman said the arrests were made over alleged public order offences.
– Metropolitan Police spokesman
Six males were arrested during the game at Millwall in relation to a banner being unfurled at the game. They remain in custody at this time."
Six people have been arrested over a banner, which reportedly attacked a footballer who was racially abused by a Millwall fan, police said.
The banner was unfurled in a Millwall section of the Lion's New Den ground during their 2-1 win against Derby County.
Bolton striker Marvin Sordell, was abused by fans while warming up for his side's game at the East London club's stadium on 6 October.
A 13-year-old boy was banned from the ground.
Britons think that racism is widespread in national football, and a majority feel it will be impossible to eradicate it completely, according to a poll.
After incidents involving Chelsea's John Terry, Liverpool's Luis Suarez and now alleged comments by referee Mark Clattenburg, the survey revealed four out of ten respondents agreed that racism is widespread in English football, an increase on 31 percent from June 2012.
57 percent said it would be impossible to eliminate racism from football but nearly two thirds (62 percent) said harsher penalties for racist behaviour would reduce the number of racist incidents, according to the ComRes poll for the Sunday Mirror.
After Mark Clattenburg was accused of using "inappropriate language" by Chelsea during last week's match against Manchester United, 62 percent of respondents said referees' conversations with players should be recorded.
– Rio and Anton Ferdinand
On the issue of Kick it Out, we would like to go on record to say what fantastic work they have done in the past regarding education and awareness.
However, times change and organisations need to change with them. We are more than happy to join the discussion, privately, to make Kick it Out more relevant in its fight to stamp out racism in football.
Although we have been left disappointed by the PFA and the FA's actions over the last year, as a family, we are committed to working with football's existing organisations towards the betterment of the game and to achieve immediate action.
In a wide-ranging statement released by the Ferdinand's management team, NEW ERA GLOBAL SPORTS, the pair have expressed their desire to "work with football's existing organisations towards the betterment of the game and to achieve immediate action".
In addition, they have claimed the Kick it Out organisation, whilst doing good work in the past, needs to change and have offered to work with it to make it "more relevant in its fight to stamp out racism in football".
The statement said: "It has been a year since the incident at Loftus Road. During that time, some of the deep divisions that exist in football have been exposed.
"In the coming months there will be ongoing discussions, we are sure, on finding a way forward.
"We intend to participate in these discussions, along with numerous other current and ex professionals of all races, from the grass roots upwards, across the football community as a whole."
Players' chief Gordon Taylor has announced a six-point action plan to deal with racism in football after criticism from some members.
The PFA chief executive says the union wants tougher penalties for racist abuse including making it potentially a sackable offence, culprits ordered to attend awareness programmes and a form of the NFL's 'Rooney rule' to boost the number of black coaches and managers.
The Manchester United defender Rio Ferdinand appears to have rubbished newspaper reports that he was planning to launch a breakaway union to protect the interests of black footballers.
Don't believe all u read.