Westminster leader Ian Blackford said a “looming” trade war with the US demonstrates the weakness of the special relationship, as he also criticised the Prime Minister for being “pushed around” by “hard Brexit” ministers ahead of the G7 summit.
Mrs May defended her Government’s approach before insisting the relationship between the two countries continues to be strong and will endure in the future.
She also highlighted the need for “continued dialogue”, adding US President Donald Trump has been warned the EU will take countermeasures in response to his steel and aluminium tariffs but a “continuous tit-for-tat escalation” would not be in the interests of anybody.
Speaking in the Commons, Mr Blackford said: “Before going to Ottawa, the Prime Minister was pushed around by her hard Brexit-supporting ministers - some might say she was trumped.
“The looming trade war with the US demonstrates the weakness in the so-called special relationship.”
Mr Blackford went on: “Doesn’t the Prime Minister agree that following the chaotic summit she attended at the weekend, that her Brexiteer sidekicks’ belief that this Government can secure a trade deal with the US post-Brexit is simply delusional?”
Mrs May, in her reply, said the Government has committed to having an independent trade policy to put in place trade deals around the rest of the world, adding agreements will be “firmly” in the interests of the UK.
Labour former minister Diana Johnson also asked: “Does the Prime Minister think that the special relationship is stronger or weaker with President Trump in the White House?”
Mrs May replied: “I think that the special relationship between the United Kingdom and the United States continues to be strong, and it continues to be strong and will endure and continue to be strong in the future.
“What it does enable us to do, the nature of the relationship is such that when we disagree with the United States and with the president, we’re able to tell him.”
Labour leader Jeremy Corbyn earlier blamed Mr Trump’s “America first” policy for a “failed” G7 summit.
Mr Corbyn said: “The problems facing leaders is that the White House is inhabited by a president committed to his slogan, America first.
“That has meant the dismantling of multilateral agreements, the pulling out of the Paris climate change accords and the destabilisation of the Iran nuclear deal, and now the imposition of tariffs on steel and aluminium.”
In her reply, Mrs May said: “I was very clear, I’ve been clear directly to President Trump, I’ve been clear in this House and elsewhere; these tariffs are unjustified and the European Union will take countermeasures on this.
“What we want to ensure is that we’re able to get a dialogue going forward such that we don’t simply see a continuous tit-for-tat escalation on these measures because that is in the interests of nobody.”