Farage told FOX Business' Stuart Varney the House of Commons should reject the new agreement Johnson has negotiated with the EU because it is an amended version of former Prime Minister Theresa May's proposed treaty, which was rejected three times by the U.K. Parliament.

"It's not a new deal," Farage said Thursday. "What Boris has now done is to amend it, get some changes, to put lipstick on the pig."

Farage also acknowledged that "there are some things that are better about it [and] some things that are worse about it."

If passed, the deal may hinder negotiations of a new trade agreement between the United States and the U.K., he said.

"Let me promise you, if what Boris is negotiating today goes through, it will be at least 2022 or 2023 before there’s any trade deal with the U.S.A," he said.

Farage also said that the U.K. would be trapped "forever" under Johnson's agreement "[with] environmental laws, with employment laws, even taxation is mentioned here."

If the House of Commons rejects Johnson’s agreement, Britain would be forced, under a law passed by Parliament, to request of the E.U. a further prolonging of Brexit negotiations.

"We would extend again," he said. "But I would rather extend than go for a bad new treaty that means we’ll never be free."