Boris Johnson pleaded for Conservative MPs to support his plans to override part of the Brexit Withdrawal Agreement in a Zoom call late on Friday.
The Prime Minister told around 250 Tory MPs on the video call that the party must not return to “miserable squabbling” over Europe.
He is hoping to pass an Internal Market Bill by the end of the month but faces opposition over some of its controversial elements.
The bill will be formally debated in the House of Commons for the first time on Monday.
It addresses the Northern Ireland Protocol, which is designed to prevent a hard border returning to the island of Ireland.
If written into UK law, it would give ministers the power to “disapply” rules relating to the transport of goods between Northern Ireland and the rest of the UK that would come into effect from 1 January, should the UK and EU fail to strike a trade deal.
The EU has threatened legal action should the bill be passed, while the European Parliament said it would scupper any chance of a trade deal.
Johnson has vowed to “walk away” from negotiations if a trade deal is not agreed by 15 October.
Informal talks are set to resume on Monday, while official talks commence in Brussels on 28 September.
Johnson told MPs the bill was “absolutely vital” to “prevent a foreign or international body from having the power to break up our country”.
He added that there was still “a very good chance” of a trade deal being reached and said it could look similar to the one agreed between the EU and Canada, which has no tariffs on the majority goods.
The Prime Minister did not take questions during the call, which was disrupted for several minutes by poor signal.
Conservative backbencher Sir Bob Neill said he was not reassured by the prime minister’s Zoom call.
Neill chairs the Commons Justice Committee and has tabled an amendment to the bill which would require a separate parliamentary vote on any changes to the Withdrawal Agreement.
“I believe it is potentially a harmful act for this country, it would damage our reputation and I think it will make it harder to strike trade deals going forward,” he said.