One of Boris Johnson's business secretaries insisted that the Prime Minister rightly argued that companies in Northern Ireland do not have to fill in forms after Brexit to export goods to the rest of the UK, although this is an obvious part of the exit agreement.

Kwasi Kwarteng said Johnson was "absolutely out of the money" when he told Northern Ireland exporters last week that they did not have to fill in additional paperwork, leading to allegations that the prime minister had misled the public.

In a video filmed on Thursday night in Northern Ireland, Johnson told exporters that they would not have to fill in customs declarations when sending goods across the Irish Sea. If companies were asked to do so, they should call him and I'll instruct them. Throw the form in the trash.

There will be no physical check from Northern Ireland to the UK, says Boris Johnson – video

This contradicted the view of Stephen Barclay, the secretary of Brexit, who told a House of Lords Committee that companies would have to complete "exit summary statements" for such shipments.

Kwarteng, who was asked on Sunday at Sky's Sophy Ridge Show if Barclay was wrong, said, "I think you should ask him, but I think the Prime Minister knows his deal, I mean, he has negotiated about it. "

Kwarteng rightfully told Johnson that there would be no customs forms and no checks: "As far as I know, I do not think there will be any, I think the Prime Minister is absolutely right."

Kwarteng also defended a conservative analysis in which he claimed that Labor's combined policy would cost £ 1.2 billion in five years. forwarded to sympathetic newspapers on Sunday, but declined to give a parallel sum for conservative spending plans.

He said that the total amount had been put together by "persons in …" [Conservative] Central and Independent Analysts "after Mark Sedwill, the public service chief, had blocked the publication of a separate treasury analysis of the work plans.

"You can rightly say that Mark Sedwill has blocked public service costs and that's why we have a separate analysis," said Kwarteng.

The total sum combines Labor 2017 election manifesto obligations – the party has not yet released its current manifesto – and adds other ideas such as a universal basic income and a four-day work week, some of which are by no means sure that they are part of this manifesto Manifesto of 2019.

Asked about the sum for Tory plans, Kwarteng said only that the Party's commitments are "not as astronomical and vast as the Labor sums."

When pressed for a certain amount, he added, "I will not mess with numbers."

Kwarteng also defended Johnson's comparison of Jeremy Corbyn with Stalin's treatment of the kulaks, rich peasants who were persecuted under the Soviet dictator and in many cases murdered.

Kwarteng said Corbyn's attitude towards wealth creators and entrepreneurs is similar to Stalin's. He did not believe, however, that the Labor leader was actively planning to assassinate such people.

Last week, when another minister of economics, Nadhim Zahawi, was asked by the BBC if Corbyn wanted to have businessmen shot dead, Zahawi replied, "I do not know, you have to ask him that question."

Kwarteng said, "The comparison was about philosophy and Marxism. Nobody suggests Jeremy Corbyn will line up and shoot. "

He added, "Nobody believes Corbyn will kill anyone, let's say that very clearly."