Vote Leave, the designated Out campaigning machine, frequently says that the UK gives £350m to Brussels.
Michael Gove and Boris Johnson are among those who use the statistic to make a point about how the UK loses out from membership of the EU.
But that statistic has now been slammed by the UK's statistic watchdog as "misleading".
The UK Statistics Authority said that the claim is "potentially misleading" as it doesn't factor in the UK's rebate or money that comes back from the EU.
Sir Andrew Dilnot, who heads up the watchdog, said that the UK's gross contribution to the EU in 2014 was £19.1bn, but after the rebate it was £14.7bn and the net contribution was £9.9bn.
That's £190m per week, which many may still see as too much, but is some way off the £350m figure stated.
"Without further explanation I consider these statements to be potentially misleading. Given the high level of public interest in this debate it is important that official statistics are used accurately, with important limitations or caveats clearly explained," Dilnot said.
A Vote Leave spokesman said: "As the Office for National Statistics makes clear the EU takes £350m from us every week. That is the total debit made from our national accounts.
"We get some money back but that is controlled by the EU – if we Vote Leave we will take back control of all of this money. We will be able to spend our money on our priorities like the NHS."