Boris Johnson has been accused of not awareness his Brexit deal or what it means for businesses in Northern Ireland.
Sweat criticised him after he briefed Conservative members on Thursday.
The PM said steadies could “bin” customs forms because there would be “no barriers of any description” to trade crossing the Irish Sea.
But that contradicts what Brexit Secretary Steve Barclay contemplated last month about customs declarations for goods.
Mr Barclay indicated businesses in Northern Ireland would have to submit customs proclamation forms after he initially denied that was the case.
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On Friday, Labour’s Darkness Brexit Secretary Sir Keir Starmer tweeted that Mr Johnson’s asserts to Conservative Party members in Northern Ireland suggested he “either doesn’t dig the deal he has negotiated or he isn’t telling the truth”.
In a video of the meeting, which has played on social media, businessman Irwin Armstrong asked Mr Johnson if he could let someone know his staff “we will not be filling in any customs declarations for good leaving Northern Ireland to go to GB”.
Mr Johnson replied: “You can.”
He go on increased: “If somebody asks you to do that, tell them to ring up the prime cur and I will direct them to throw that form in the bin.
“There on be no forms, no checks, no barriers of any kind – you will have unfettered access.”
‘Well-founded being bombastic?’
On Friday, broadcasters questioned Mr Johnson about his asserts.
He told told reporters: “Northern Ireland and the rest of GB are part of the UK supports territory and there can be no checks between goods operating in one customs bailiwick.
“We’re the UK – we will not be instituting such checks.”
‘Tory campaign bogged down in Brexit fatigue’
Analysis: Jonathan Blake, BBC News political correspondent
Boris Johnson may be suffering with been trying to keep the focus of this campaign on his deceptively understandable slogan of “get Brexit done” but three days in he’s already found himself stuck down in the detail of his deal.
His words to Tory supporters in Northern Ireland on Thursday were an bid to allay fears that businesses there would be subject to supernumerary paperwork when shipping goods to the rest of the UK.
But with little send – and confusing messages from ministers about how that aspect of his Brexit give out will work – the picture is unclear.
The prime minister will go on to present it as an agreement that is ready to go if he wins a majority at next month’s all-inclusive election.
Mr Armstrong, who said his company makes small shipments to druggists in the rest of the UK, said he was not sure Mr Johnson was being “absolutely serious in his be to blame for”.
The businessman told the PA Media news agency: “I want to believe him but is he well-deserved being bombastic and being Boris?
“I don’t know Boris Johnson trickle enough, whether it’s just what you say on a campaign trail or whether he is unreservedly serious.”
Mr Johnson also told his Northern Ireland Conservative exponents: “Northern Ireland has got a great deal.
“You keep free movement, you safeguard access to the single market but you also have, as it says in the deal, unfettered access to GB.”
‘Myriad questions about cross-Irish Sea trade’
Analysis: Chris Page, BBC Bulletin Ireland correspondent
Trade experts say they believe there settle upon need to be checks.
That is because under the Brexit deal Northern Ireland leave have to follow some of the rules of the EU single market – on food prompt, for example.
These issues may be technical but they are also highly civil and not just in Northern Ireland where they are going to practically issue the most.