May was asked bluntly by Liberal Democrat leader Vince Cable what point there was in the G7, but May pointed to a number of achievements made during the summit.
The leaders of the world's richest democracies have promised some kind of compromise statement despite their deep divisions on trade.
Even a boilerplate communiqué, which reiterated the rich nations' commitment to free and fair trade, was undermined at the last minute, when American president Donald Trump repudiated the agreement.
German Chancellor Angela Merkel described his change of heart as "sobering and a little depressing".
Peter Navarro, a White House trade adviser, has apologised after saying "there's a special place in hell" for Canadian Prime Minister Justin Trudeau, who is in a trade dispute with President Donald Trump.
Trump went on to say that the USA gets "unfairly clobbered" on trade despite "protecting Europe at great financial loss".
Monday's symbolic House vote was held after Mr. Trump criticized Mr. Trudeau over the weekend for vowing to retaliate against tariffs recently imposed by the US on Canadian steel and aluminum products.
In addition to rejecting the insults aimed at Mr. Trudeau, the measure passed Monday said that lawmakers "strongly oppose the illegitimate tariffs imposed by the USA government against Canadian steel and aluminum workers" and "stand in solidarity with the Government of Canada in its decision to impose retaliatory tariffs".
"Based on Justin's false statements at his news conference, and the fact that Canada is charging massive Tariffs to our U.S. farmers, workers and companies, I have instructed our U.S. Reps not to endorse the Communique as we look at Tariffs on automobiles flooding the U.S. Market!"
"To say Canada stabbed the president in the back". It is up to the diplomats now to ameliorate the relationship between the two trading partners.
However Trump was at odds with numerous other global leaders, suggesting Russian Federation be re-admitted to the group.
He stressed the countries have to work together.