The campaign to get Britain out of the EU has launched a contest to win £50m - if you can correctly predict the result of all 51 games in the Euro 2016 football championships.
If no one manages that then there is a £50,000 prize for the person who gets the most consecutive games correct.
Vote Leave has taken out an insurance policy to fund the contest.
But Britain Stronger In Europe say it is a "con" - with the odds of winning a sextillion to one.
The £50m represents the amount Vote Leave says Britain sends to the EU a day, a claim disputed by its critics.
The argument that Britain sends £350m a week to the EU has proved controversial because it does not take into account the rebate that the UK gets on its payments to the EU.
A Vote Leave source said the football contest could be a "game changer" for the campaign because it would allow them to gather the contact details of thousands of potential voters, many of whom would not normally be interested in the referendum.
Anyone entering will have to rate themselves on a scale of one to five as to whether they are more likely to back continued membership of the EU.
The campaign admits that the chances of winning the top prize are slim - but says it is "worth a punt".
But Will Straw, executive director of Britain Stronger In Europe, said the long odds were the same as those for Vote Leave "coming up with a coherent vision for what life would look like outside the EU".
He added: "Once again Vote Leave put wild guesswork at the heart of their campaign and it is the British people who they are asking to take the risk."
Hosts France take on Romania in the first game of Euro 2016 on 10 June, with England and Wales in action the following day.
Vote Leave's campaign director Dominic Cummings said: "This is the chance of a lifetime - just imagine what you could do with the £50m we send to the EU every single day.
"We want everyone to have the chance to win the sort of money most people can only dream of, unless they are a banker or a Euro MP."
You are staggeringly unlikely to win this competition.
There are 36 games in the group stages of the tournament, when there could be a victory for either side or a draw.
Then there are 15 knockout games, which cannot be drawn.
The odds of picking all 51 games randomly are one in 5,000,000,000,000,000,000,000, which is a bit better than the odds of guessing the mobile phone numbers of the next two strangers you see in the street.
Now, your in-depth knowledge of European football may tip the odds more in your favour, but remember you also have to guess which teams will qualify from the group stages, which may go down to goal difference or even goals scored.
The competition is a based on a similar contest in the US, run by billionaire Warren Buffett, one of the world's richest men, involving the annual men's NCAA basketball tournament known as March Madness.
Vote Leave says the contest is free to enter and is open to anyone who is over the age of 18 who is registered to vote in the EU referendum.
Entrants must supply their telephone number, email address and home address to qualify for the prize.
A spokesman for the Electoral Commission said any money spent on the contest would have to be reported by the campaign, but added: "Vote Leave indicate that the £50m prize would be paid by an insurance company and not by them."
The chairman of the UK Statistics Authority has again rebuked Vote Leave over its £350m a week claim.
In a statement on the authority's website, Sir Andrew Dilnot said that he was "disappointed" that the campaign group continued to claim the full amount could be spent in the UK, saying it "undermined trust in official statistics".