Calling the EU “unconstructive” on the issue, the Conservative peer said it was obvious that the protocol needed fixing.
Mr Frost also backed controversial plans by Foreign Secretary Liz Truss to scrap parts of the arrangement and insisted there was no need for a trade war.
The EU has threatened to retaliate with “all measures at its disposal” if the UK proceeds with legislation overwriting sections of the protocol.
Critics have warned it would be an “unacceptable breach” of international law and would fuel distrust of Britain.
The treaty agreed on by the UK and EU to maintain the Irish land border has created economic barriers on the movement of goods between Britain and Northern Ireland, causing resentment and anger among unionists and loyalists.
The row has created an impasse in efforts to form a devolved government administration in Belfast.
The UK is planning to introduce separate “green” and “red” lanes for goods travelling between Britain and Northern Ireland, drawing a line between those destined to stay within the UK and those heading to the Republic of Ireland and beyond.
“We are told that fixing very obvious problems with the Northern Ireland Protocol will cause, it is said, ‘huge and irreparable damage to our foreign relations and international reputation’," Mr Frost said, speaking in the House of Lords for the first time since resigning from the frontbench last year.
"I don’t agree with that. Any observer can see that protocol is undermining the Belfast Agreement, it’s weakening the government’s ability to govern Northern Ireland. Any observer can see it needs fixing.
“There is no need for a trade war. If it comes, it won’t be our choice, I guess. Some argue that the war in Ukraine makes it the wrong moment to address this question.
"On the contrary, I think the great events that are under way make it all the more important for us to fix the issues that are dividing western countries.
“To me it makes it all the more surprising and disappointing that the EU will not help us solve this problem and continues to be so unconstructive.
“Of course it is right that we should remain open to negotiation; a negotiated settlement would still be better.
“But in my experience only clarity about objectives and robustness in presenting them gets results, and knowing the foreign secretary I am sure that is how she will intend to proceed.”
However, former national security adviser Lord Ricketts warned: “Seen in the perspective of a major war in Europe, both the substance and timing of that are massively ill-judged, in my view.
“If pursued it will confirm the view in European capitals that Britain is not to be trusted.”
“Let’s back down from the brink of a major breach with the EU and let’s work together with EU countries for peace and stability in Europe,” he added.
“This is not the time to drift into a confrontation over the implementation of the Northern Ireland Protocol or to be threatening to take unilateral action to set aside explicit provisions in the Withdrawal Agreement. That is the height of irresponsibility,” said Lord Hannay of Chiswick, who served as UK ambassador to both the EU and UN.
“The breaking of that treaty by the United Kingdom is an unacceptable breach not just of the law but the law of nations and what is higher in law than the law of nations?” Said former terror law watchdog and leading lawyer Lord Carlile of Berriew.
Independent crossbencher and former ambassador Lord Kerr of Kinlochard, who was author of the Article 50 mechanism by which the UK left the EU, warned the Lords could reject legislation that sought to unilaterally make changes to the protocol.
“I would like people to believe that, if they conclude a deal with us, then that deal is likely to stick. That makes it easier to conclude a deal," he said.
“I would like people to think it unthinkable that we would break a treaty commitment and start a trade war.
“I think this House still champions the rule of law.”