Mr Donaldson explained the withdrawal agreement which included the backstop was turned down three times by Theresa May's Government noting that it was the Government's biggest defeat in history over the previous deal.
"We talked to the police and customs".More news: UK Conservatives retain large lead over Labour
McDonald added, "Despite Mr Johnson's claims to the contrary, the path he is leading would lead us to a hard border".
Johnson, who insists Britain must leave the 28-nation European Union in just over 50 days, come what may, said in Dublin that leaving without an agreement on divorce terms "would be a failure of statecraft for which we would all be responsible".
Almost eight in ten unionists believe the backstop "separates Northern Ireland from the rest of the United Kingdom in unacceptable ways and the government should not agree to any deal that includes it".
"Let's not put this down to just simply a Unionist concern when there isn't a single unionist elected representative who supports the backstop".More news: Taylor Swift suspect charged in Trump golf course damage
"What we're trying to do is to agree alternative arrangements that will make the backstop unnecessary".
The Department for Transport produced a "factual paper on the subject" after conversations between the DUP and former Secretary of State for Transport Chris Grayling.
Johnson reportedly wants to find out where the money for the project could come from, as well as "the risks around the project" - which apparently include "WW2 munitions in the Irish Sea".
Number 10 has insisted it has not commissioned any work on the project, and that the work was done by the civil service during the Tory leadership election as possible schemes for a new prime minister to pursue.More news: Ship overturns near Georgia port; 4 crew members missing