Humanitarian organisation Oxfam has urged G7 countries to pay up nearly half of the United Nations (UN)'s $6.3bn appeal to avoid unprecedented famine.

Leaders of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States, are expected to meeting in Taormina, Sicily on 26 and 27 May, as millions are at risk of starvation and famine across the Horn of Africa, Nigeria and Yemen, due to lack of rain and prolonged insecurity driving people away from their fields, jobs, food and markets.

Ahead of high-level meeting, Oxfam said the G7 nations should take the lead in fighting the famine with a massive injection of aid, and press for immediate ceasefires and inclusive peace processes to quash the long-standing conflicts that are driving the food crisis.

If each G7 government contributed its fair share to the UN's appeal for $6.3bn to prevent the crisis from spiralling out of control in all four affected countries, Oxfam said it estimates that this would raise almost half of the total required, or $2.9 bn. Only 30% of the UN appeal has so far been funded across Nigeria , South Sudan, Somalia and Yemen.

"Political failure has created this crisis and now political leadership is needed to end the agony of hunger. The world's most powerful leaders must not walk away from Taormina without providing emergency funding and clear solutions to tackle the root causes," Ed Cairns, senior policy adviser at Oxfam, said in a statement released on 24 May.

Collectively the G7 nations have provided $1.7bn so far – just under 60% of their fair share. Oxfam highlighted how the UK has already funded its fair share of aid to South Sudan, Yemen and Somalia.

"Britain is doing more than most, but needs to deliver on its promises to provide more help to people at risk of starvation in Nigeria. It is hugely regrettable that none of the G7 nations has provided its fair share of funding to all four countries at risk of famine while thousands of people are already dying from disease and extreme hunger."

France, Italy and Japan have so far failed to reach their fair share in any of the affected countries, where 30 million people are now experiencing severe hunger – of whom 10 million are facing emergency and famine conditions.

In addition to funding the UN appeal, Oxfam also recommended G7 leaders should focus on building smallholder farmers' resilience in order to reduce needs over time.