LONDON — UK Foreign Secretary Yvette Cooper called on allies to secure the reopening of the Strait of Hormuz within weeks to allow fertiliser shipments to resume, speaking at the Global Partnerships conference in London. She also announced a package of UK health, science and development investments aimed at preventing a worsening food crisis.

The war in Iran has frozen shipments of fertiliser through the strait, creating a supply crunch that has damaged farming in the UK, Europe and the US and is affecting developing countries more severely where farmers cannot afford the higher prices. The World Food Programme estimates that almost 45 million more people could fall into acute food insecurity if the Iran conflict does not end by the middle of this year.

Cooper said global fertiliser supplies must be freed up within weeks to avoid disaster, with harvests suffering and food prices rising. "Iran's continued closure of the strait of Hormuz while the agricultural clock is ticking shows why we need urgent global pressure to get the strait reopened, fertiliser and fuel moving, and ease the costs of living pressures," she said.

"Instability abroad affects us here at home, from energy prices to food security. Building resilience abroad makes the UK stronger," Cooper said.

The conference is jointly hosted by the UK and South African governments and supported by the Children's Investment Fund Foundation. Cooper will announce a new health partnership to support children injured in Gaza, additional support for health systems to develop medicines and vaccines more quickly, and a £200m investment in science and technology. British International Investment will announce £4.6bn for climate investment in emerging markets, and the UK will provide $250m to the African Development Bank and increase its shareholding in the Inter-American Development Bank.

Richard Hawkes, chief executive of Oxfam GB, said: "Unlawful attacks by the US and Israel on Iran have killed, injured and displaced civilians across the region." He added: "Retaliation from Iran, which includes the closure of the strait of Hormuz, is driving up the cost of food and fuel and putting basic necessities out of reach for millions of people."

"UK aid cuts – set to be the steepest of any G7 country this year – also risk deepening global instability and inequalities," Hawkes said. "The government must reverse the cuts and start taxing the super-rich and biggest polluters to help pay for the fight against poverty and inequality."