The rules-based order must be defended, she said, and disputes could not be solved by nations taking “unilateral actions against their partners”.
Jeremy Corbyn said Donald Trump was to blame for the summit’s “failure”.
The summit in Canada ended in disarray after the US President retracted his support for the communiqué agreed by G7 leaders and then criticised Canadian prime minister Justin Trudeau on social media.
In a statement to MPs on the summit, Mrs May praised Mr Trudeau’s “skilful” handling of proceedings and said the leaders had established “common ground” on a range of matters.
On trade, said she had been “very clear” that US tariffs on European steel and aluminium imports were damaging and dialogue was needed to ensure the dispute did not escalate into a full-blown trade war.
Multilateral action was needed to prevent “tit-for-tat” reprisals, she said, adding that the concerns of countries about unfair trade practices must be “addressed not ignored”.
