Lineker, 57, described Brexit as a “mess” and threw his support behind the People’s Vote campaign group, who seek a vote on the final deal with the EU.
That group will hold a series of rallies across the UK in a desperate bid to return to the voting booth over Brexit.
And Lineker said he is backing the move over the “bewildering and worrying” prospect of leaving the EU with no deal.
The Match of the Day BBC presenter said in a statement: “I spent most of the last few weeks totally focused on a fantastic World Cup.
“But it was impossible to avoid what was happening in the Brexit debate back home. Now I’m back I find the whole thing more bewildering and worrying than ever.
‚ÄúThis is one of them. I am not a politician but I know when something is going wrong and right now Brexit feels like it is going very wrong indeed‚ÄĚ
“Whether you voted Leave or Remain, did anyone really vote for the mess we seem to be in, let alone the prospect of no deal with all the terrible consequences attached to that?
“There are some things in life that, even for someone like me, are more important than football.
“This is one of them. I am not a politician but I know when something is going wrong and right now Brexit feels like it is going very wrong indeed.
“The politicians seem unable to resolve the problem the people gave them in voting to Leave.
“That is why I think there should be a People’s Vote on the final deal, and why I am sending best wishes and good luck to the campaigners who will be stepping up the pressure over the summer.”
His statement drew a scathing response on Twitter ‚Äď where he has actively voiced opposition to Brexit in the past ‚Äď as people told him to stick to football.
One said, tongue-in-cheek: “Gary Lineker backing a second referendum.
“That’s incredible news. He’s so knowledgeable about politics and world affairs. #Joker #Slownewsday #Sticktofootball.”
Another added: “So presumably Gary Lineker, if we have a second referendum and Remain wins, we get another one a few years later then?
“Let’s just have EU referendums every four years until the stupid people vote the ‘right’ way.”
One even ranted: “Mr Gary Lineker, nobody gives a f*** what you think on Brexit. Stick to football as you’re good at that.”
But elsewhere the ex-Leicester striker drew praise for his public rally.
A fan wrote: “Well said Gary Lineker. It takes courage to put your head above the parapet knowing you’ll get abuse from trolls and Brexit media.
“He’s well off, he doesn’t need to risk his popularity, even more credit to him for speaking out.”
Another hailed: “Well done Gary Lineker. More people like you need to stand up and be counted, including most of our utterly spineless politicians who agree with you fear for their party careers if they follow their principles.”
British Prime Minister Theresa May has rejected calls for a second referendum since the vote in June 2016 and her appointment as Tory leader the following month.