The most significant feature of the bus was the claim on its side which stated that Britain sent £350 million to the European Union every week. This was based upon the
Treasury's estimation of the gross amount of money that the UK contributed to the EU in 2014, totalling to £18.8 billion, or in 2015, totalling to £17.8 billion, or £342 million per week. Dominic Cummings intended that use of the figure would stoke up arguments concerning future payments to the EU, which would be beneficial for the Vote Leave campaign. On 23 May, leading Brexit campaigner
Andrea Leadsom repeatedly cited a "£10 billion independence dividend", which was her estimate of Britain's net contribution to the EU when taking into account the rebate as well as EU funding to the UK, on
Newsnight. Other key people in the Vote Leave campaign began to use this figure instead. On 27 May, the
UK Statistics Authority chair
Andrew Dilnot made a stronger statement against Vote Leave, stating that the continued use of the figure was "misleading and undermine[d] trust in official statistics".
Full Fact, a
fact-checking organisation, argued in June that the £350 million estimation did not take into account Britain's
rebate, which had been negotiated under
Margaret Thatcher in 1984 to be significantly lower than the usual 1% of national
gross domestic product paid by other member states. As the UK's budget rebate to the EU in 2015 was £4.9 billion, an estimation involving the rebate would total to £12.9 billion, or £248 million per week, significantly less than £342 million per week. This rebate was deducted before any payment to the EU was made. An article by The Guardian further argued that the £350 million figure also ignored EU spending on the UK, estimated at £4.4 billion in 2015, as well as injections from the EU into the UK's private sector, which was £1.4 billion in 2013. It thus argued that the net figure was actually £7.1 billion or £136 million per week.
The Guardian also disputed the use of the word "send" on the bus, and the claim that this money would be available to spend on the NHS if the UK left the EU. On 9 June,
Nicola Sturgeon of the
Scottish National Party stated in a TV debate that the continued existence of the £350 million claim on the side of the campaign bus was a "scandal" and accused Johnson of "driving around the country in a bus with a giant whopper painted on the side", and
Angela Eagle of
Labour told Johnson to "get that lie off your bus!" Johnson repeatedly defended the use of the number. Conservative MP Dr
Sarah Wollaston defected from Vote Leave to support the Remain campaign the same day, citing that she no longer felt comfortable with Vote Leave due to the £350 million claim being false.
After the referendum Following the referendum, a number of prominent Vote Leave campaigners began to distance themselves from the £350 million figure, while others insisted it was correct. In 2017,
Dominic Cummings, leader of the Vote Leave campaign, stated that "all our research and the close result strongly suggest[ed]" that Remain would have won if Vote Leave had not used the £350 million NHS claim, and that "It was clearly the most effective argument, not only with the crucial
swing [vote] but with almost every demographic". In January 2018, Boris Johnson said in an interview with
the Guardian that "there was an error on the side of the bus. We grossly underestimated the sum over which we would be able to
take back control", and also argued that the UK's contributions to the EU were already at £362m per week in 2017–18 and would annually rise to £410m, £431m, and then to £438m by 2020–21. A study by
King's College London and
Ipsos MORI, published in October 2018 found that 42 percent of people who had heard of the £350 million claim still believed it was true, whereas 36 percent thought it was false and 22 per cent were unsure. The study also found that criticism of the claim by the UK Statistics Authority and others had not changed belief in the claim since before the referendum. In June 2019, a private prosecution brought against Johnson by businessman Marcus Ball concerning Johnson's £350 million claim, following a crowdfunding campaign of £200,000 to finance the legal action, was thrown out by the
High Court after five minutes of deliberation by two judges. Johnson's lawyers had stated that the application was a "political stunt" and that he wanted to "undermine the referendum result", whereas Ball said he had a "duty to [his] country to keep fighting lying in politics and [he took] it bloody seriously." In the ten years following the referendum, spending on the NHS actually increased (in real terms) by £1.1bn per week, though it is not possible to quantify how much of this (if any) might be attributed to savings in EU contributions. == Imitative buses ==