Campaigners have urged Britain's overseas territories to expose the true owners of shell companies set up on their shores to curb illicit financial flows that deprive poor countries of billions of dollars.

As the UK government and leaders of the overseas territories hold their annual ministerial meeting, the NGOs ActionAid, Christian Aid and War on Want called on the British Virgin Islands, Bermuda, the Caymans and other territories to create a public register of owners of hundreds of thousands of shell companies.

Britain's prime minister, David Cameron, announced last month that a central register of company beneficial ownership would be open to the public, and campaigners want the overseas territories (countries nominally still under the UK's auspices, but in practice self-ruled) to follow the UK's lead.

"Now the government should lead the way … in promoting such public registers as a standard for other countries," said Barry Johnston, from Christian Aid. "The overseas territories, whose governments are currently looking at this issue, have the opportunity to lead from the front on this new standard. But, ultimately, the responsibility for the global impacts of these islands lies with the UK government."

Tax evasion and illicit financial flows have become increasingly important for rich and poor countries. The UK and US have shown impatience towards companies such as Google and Apple as they manipulate the system to their maximum advantage. But most African countries, with weak tax regimes, are by far the biggest losers.

According to the African Development Bank and Global Financial Integrity, a US research organisation, Africa has been a long-term net creditor to the rest of the world, losing $597bn-$1.4tn in net resource outflows between 1980 and 2009 after adjusting recorded transfers for illicit financial outflows.

The US and EU have put pressure on tax havens to share information about the fortunes hidden on their shores, and, as a result, several of the most clandestine jurisdictions, including Switzerland, are preparing to share such information.

But African experts have pointed out that the increased co-operation is between, and to the benefit of, developed countries. Poor countries risk being left in the dark, with no access to information about the financial resources taken from them, Zitto Kabwe, a Tanzanian MP, argued recently.

Wealthy and developing countries must agree to an automatic and unconditional exchange of information about tax, he said, adding that global rules to ensure multinationals report on a country-by-country basis were also vital, to insist they pay the correct amount of tax in each country.

Leaders at the G8 summit in June made commitments towards a fairer and more transparent global tax system. For their part, the overseas territories promised to sign up to the international system through which governments exchange tax information – the Organisation for Economic Co-operation and Development (OECD) multilateral convention, which would allow poor countries access to more information on who owns what and help them assess how much tax they are rightfully owed.

"We acknowledge the progress made on G8 commitments, including the move by the overseas territories to join the multilateral convention," said Oxfam's senior policy adviser, Claire Godfrey. "We want to see them put this into practice as a matter of urgency, because doing so will help other countries, including the poorest, to catch up with tax evaders."

Campaigners also highlighted a range of other measures that overseas territories would need to take before they can shed the reputation of being tax havens. These include extending the automatic tax information sharing agreements already reached with the UK to other countries, undertaking an analysis of their negative impacts on the tax regimes of developing countries, increased transparency on financial flows, and access to company accounts.

The Foreign Office, which has organised the three-day ministerial meeting, said the overseas territories have already done much to make a difference. "The overseas territories are concluding automatic tax information exchange agreements with the UK and the US and have committed to play an active part in the new pilot initiative of multilateral automatic tax information exchange launched by the UK, France, Germany, Italy and Spain," said a spokesman. "All of the overseas territories with financial centres have published action plans on beneficial ownership."

The Department for International Development (DfID) said last week it would provide developing countries with expert advice to boost tax revenues. New support will fund four projects to improve revenue collection and help authorities combat tax evasion and avoidance.

This will include establishing an OECD database of expert tax inspectors who can be deployed to developing countries to advise on complex audits. It will also include advice on transfer-pricing rules that will make it harder for multinationals to avoid tax. The £6m of support could help to boost revenues by up to £100m over the next four years, according to DfID.