Boris Johnson spent tens of millions of pounds on a Brexit preparedness campaign which did not actually make the public better prepared for Brexit, the UK's official spending watchdog has found.

The UK government budgeted £100 million for the campaign, which included billboards across the UK and multiple newspaper adverts.

However, the National Audit Office found that members of the public were no more likely to seek out information about preparing for Brexit at the end of the campaign than at the start.

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Boris Johnson's government spent £46 million on a "Get ready for Brexit" advertising campaign which didn't actually make the public any better prepared for Brexit, the UK's official spending watchdog has found.

The UK government budgeted a total of £100 million for a public billboard, newspaper, and social media campaign, promoting Britain's then planned exit from the European Union on October 31 2019.

However, the National Audit Office found that by the time the campaign was brought to an end, just 34% of the public were likely to seek out information about preparing for Britain's exit, which was broadly unchanged from the start of the campaign.

The watchdog found that while overall the public were made aware of some things they may need to do before Brexit, "the Cabinet Office could not demonstrate that the air campaign resulted in significantly better preparedness."

The plan was the most expensive of four options considered by the government, with the least expensive option being simply to do nothing.

The NAO suggested that the effectiveness of the campaign may have been hindered by the public's awareness that the October 31 Brexit deadline promoted by the campaign was unlikely to be kept.

By the time of the campaign's launch, the UK parliament had already repeatedly voted to delay Brexit and avoid leaving the EU without a deal.

"The impact of the campaign is likely to have been reduced by the public's reading of political events in the weeks leading up to 31 October and the likelihood of a no-deal exit," the watchdog found.

A UK government spokesperson defended the campaign.

"The Get ready for Brexit campaign reached 99.8% of the UK population and the NAO's findings showed increased public awareness of the action they needed to take to be ready to leave the EU," they said.

"Not undertaking the campaign would have risked significant and unnecessary disruption to businesses and to people's lives."