A top conservative United Kingdom lawmaker on Thursday warned Democratic nominee Joe Biden that the U.K. does not need "lectures" on Brexit and issues related to Northern Ireland after the Democratic presidential nominee put conditions on a free-trade deal between the two countries.

“We don’t need lectures on the Northern Ireland peace deal from Mr. Biden,” Iain Duncan Smith, a Conservative Party MP and former leader of the party, told The Times of London.

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“If I were him I would worry more about the need for a peace deal in the USA to stop the killing and rioting before lecturing other sovereign nations,” he said in reference to the violence that has engulfed the United States over the summer.

Biden on Wednesday echoed fears in Washington that a new U.K. Brexit bill, which would override the Withdrawal Agreement signed with the European Union last year, could result in a hard land border between Northern Ireland (part of the U.K.) and Ireland (an E.U. member) -- and destabilize the peace brought by the 1998 Good Friday Agreement.

“We can’t allow the Good Friday Agreement that brought peace to Northern Ireland to become a casualty of Brexit,” Biden tweeted on Wednesday. “Any trade deal between the U.S. and U.K. must be contingent upon respect for the Agreement and preventing the return of a hard border. Period.”

His tweet included a letter sent by lawmakers in the House Foreign Affairs Committee, who wrote to Prime Minister Boris Johnson this week, urging him “to abandon any and all legally questionable and unfair efforts to flout the Northern Ireland protocol of the Withdrawal Agreement and look to ensure that Brexit negotiations do not undermine the decades of progress to bring peace to Northern Ireland and future options for the bilateral relationship between our two countries.”

Duncan Smith was not the only Tory MP to express annoyance at Biden’s remarks. Former Brexit Secretary David Davis told the Times: “Perhaps Mr. Biden should talk to the E.U. since the only threat of an invisible border in Ireland would be if they insisted on levying tariffs.”

In the opposition Labour Party, however, MPs were more critical of the government than Biden.

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“This shows the scale of the damage the government has done to Britain’s standing in the world. They’ve lost trust and undermined co-operation at the moment we most need it - and all to tear up an agreement they negotiated,” Shadow Foreign Secretary Lisa Nandy said. “Reckless, incompetent and utterly self-defeating.”

A free trade deal between the U.S. and the U.K. has been on the cards for years since Britain voted to leave the E.U. in 2016, and the Trump administration has been extremely supportive of such a deal. It was barred from making such deals as an E.U. member

But as negotiations between the E.U. and the U.K. for its own deal have stalled, the U.K. said it believes that the E.U. is going to use the Withdrawal Agreement -- which includes measures to keep the border between Northern Ireland and Ireland open -- to impose a hard trade barrier between Northern Ireland and Britain.

“We are being told that the E.U. will not only impose tariffs on goods moving from Great Britain to Northern Ireland, but that they might actually stop the transport of food products from GB to NI,” Johnson said in an op-ed on Saturday.

This has led to fears that the U.K. may in fact impose a barrier between Northern Ireland and Ireland itself, undermining the 1998 peace accord. U.K. Foreign Minister Dominic Raab pushed back on Wednesday, claiming that the bill was precautionary and defensive.

British Foreign Secretary Dominic Raab speaks at a press conference with Secretary of State Mike Pompeo at the State Department, Wednesday, Sept. 16, 2020 in Washington. (Nicholas Kamm/Pool via AP)

“Our commitment to the Good Friday Agreement and to avoid any extra infrastructure at the border between the north and the south is absolute,” he said at a press conference in Washington, alongside Secretary of State Mike Pompeo.

Raab also met with Speaker Nancy Pelosi and Ways & Means Committee Chairman Richie Neal, who again warned there would be “no chance” of a deal if the Good Friday Agreement was undermined.

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“In our meeting today with the Foreign Secretary, Chairman Richie Neal and I welcomed his assurances but reiterated the same message that we delivered to the leaders of the U.K. in London last year: if the U.K. violates its international agreements and Brexit undermines the Good Friday accord, there will be absolutely no chance of a U.S.-U.K. trade agreement passing the Congress,” Pelosi said in a statement.

The Trump administration has been more positive, however. Pompeo said on Wednesday that the U.S. has “great confidence that they will get this right in a way that treats everyone fairly and gets a good outcome for what it was the people of the United Kingdom voted for several years back.”