The NAO report was published amid growing political uncertainty over the timescale by which Britain might leave the EU.
An assessment by the NAO on Britain's preparedness for Brexit, released last week, stated: "On 1 September 2019, the government launched a major communications campaign to help individuals and businesses prepare for EU exit, including newspaper and television adverts, improved guidance, and direct engagement with industry."
But it warned: "However, at this late stage and with ongoing uncertainty about the prospect of no deal on 31 October, this may have limited impact."
The NAO report highlights the uncertainty that surrounds Brexit, stating that "it is impossible to know exactly what would happen at the border in the event of no deal".
And the cross-government Border Delivery Group has warned that a key priority of having a "comprehensive programme of trader communications" is rated red, it said.
This means that successful delivery appears to be unachievable, with major issues that do not appear to be manageable or resolvable.
The NAO report stated: "The government is heavily dependent on third parties being well-informed and making changes to their systems and behaviours. This includes traders, hauliers and passengers."
It added: "If these groups are not prepared for the controls which EU member states are likely to impose this may lead to queues at the border."
The questions over the effectiveness of the government's Brexit comms come just weeks after the £100m 'Get ready for Brexit' campaign was launched.
It was described by Guardian columnist Suzanne Moore last week as "mystifying in its utter uselessness".
She added: "This is all billed as a public information campaign but it is devoid of information and is simply publicly-funded government propaganda."
Just saw an advert telling me to get ready for #Brexit on the 31st oct. Perhaps we should've spent that money on the NHS instead? #Conservatives #VoteLeave #LabourParty #LibDems #wasteofmoney #BrexitShambles— David Hemsted (@davidhemsted) October 22, 2019
The government spent about £411,000 in August on its Brexit campaign, but has yet to publish details of how much it has spent on the campaign since it was launched last month.
TV and radio spots for the campaign, which is being led by Engine, with Manning Gottlieb OMD handling media buying, are still being broadcast stating that the UK will leave the EU on 31 October.
Dear @LBC @NickFerrariLBC ... your station is still carrying the "get ready for Brexit on 31st October" ads, part of a £100 million waste of taxpayers money ... what is your company's position on carrying untruthful advertising?— John Spiers Esq. #GTTO (@squeezyjohn) October 23, 2019
The 'Get ready for Brexit' website makes no mention of the fact that the EU is considering granting an extension, and states: "If the withdrawal agreement is not signed by the UK and the EU, the UK could still leave with no deal on 31 October 2019."
Failing to deliver
The years since Britain voted to leave the EU in 2016 have been punctuated by missed deadlines and extensions to the withdrawal process.
Failure to deliver on Brexit has already forced one prime minister from office, and Boris Johnson's future in the role could also depend on the outcome.
Change of tone
Earlier this week it emerged that the 'Get ready for Brexit' campaign had quietly dropped the message of 31 October as the date Britain is due to leave the EU, with its website promoting a more cautious message: "We could still leave with no deal on 31 October."
And last night Johnson's quest to take Britain out of the EU by the end of this month suffered a fatal setback, when his timetable to get the Withdrawal Agreement Bill through Parliament was rejected by MPs.
Although he had promised to pull the bill if he lost the vote on the timing of the process, Johnson instead opted to "pause" proceedings pending the EU's formal decision on granting an extension.
Donald Tusk, president of the European Council, has already stated that he is recommending that EU leaders grant one.
Following PM @BorisJohnson’s decision to pause the process of ratification of the Withdrawal Agreement, and in order to avoid a no-deal #Brexit, I will recommend the EU27 accept the UK request for an extension. For this I will propose a written procedure.— Donald Tusk (@eucopresident) October 22, 2019
In a bid to break the impasse in Parliament, Johnson has repeated his desire to have a general election, but this is something that he cannot force through without parliamentary support.
For all the political complexities, the bottom line is that the Brexit deadline has shifted yet again – in what is a political moving target – and Parliament remains deadlocked over the issue.
The Cabinet Office has been approached for comment.
In its latest factsheet on the campaign, released earlier this month, it stated: "The Government's policy is that the UK leaves the EU on 31 October. It is the job of civil servants to support Ministers in delivering that policy and to help Ministers communicate that policy factually."
The factsheet added: "It remains the case in law that the UK is set to leave the EU on 31 October 2019. This is the date fixed by the EU Treaties and by Act of Parliament."
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