Labour would restore Britain’s commitment to international law, David Lammy will say, taking aim at the Government’s “cavalier” record on obeying the rules.

The shadow foreign secretary will commit to restoring a duty for ministers to comply with international law, an obligation which was removed by the Cameron-era government.

Mr Lammy will claim the Government has flouted its international obligations on several occasions over recent years.

As prime minister, Boris Johnson threatened to rewrite Northern Ireland’s post-Brexit trade arrangements without agreement from the EU.

The former prime minister’s actions led to a chilling of the relationship between Britain and the trade bloc.

Meanwhile, the Government’s determination to tackle the small boats crisis through the Nationality and Borders Act led to condemnation from lawyers and UN officials about its humanitarian impact.

And Prime Minister Rishi Sunak last week faced calls from his own backbenches to rethink plans to ban councils from supporting the Boycott, Divestment and Sanctions movement against Israel.

Tory MPs warned that the Economic Activity of Public Bodies (Overseas Matters) Bill was not compliant with the UK’s existing foreign policy commitments on the Israel/Palestine peace process.

In a speech at the Bingham Centre of International Law, Mr Lammy is expected to say: “We live in a time in which the magnitude of the global challenges we face have never been greater and the need for compliance with international law more vital, but in the face of these challenges this Government’s attitude to international law has never been more cavalier.

“Labour will restore Britain’s influence and realise our potential by using the international rule of law as the connective tissue which binds us to other nations.

“Creating consensus around the laws that will shape the future. Protecting our world’s precarious climate and environment. Shaping the rules on new technologies in all of our interests. And ending the age of impunity that allows authoritarians to hide their stolen cash in our capital.”

Mr Lammy argued that the Conservatives had abandoned a cross-party consensus, saying: “No British government of modern times has been so brazen in its contempt for international law or brought such a litany of law-breaking legislation for Parliament to consider as this Conservative government.”

He will set out plans to reverse the decision to remove a duty for ministers to comply with international law and treaty obligations from the ministerial code.

Mr Lammy will say: “David Cameron’s decision to remove it in 2015 showed contempt. And it foreshadowed the reckless abandonment of this principle by his successors.

“With Keir Starmer in Number 10, the rules will be clear, ministers will uphold international law.”