The charity's report, Closing the Gap: Putting EU and UK Gender Politics into Practice, aims to show that women still have no voice in the development decisions that affect their lives.
The delegates, from South Africa, Bangladesh and Central America, will try to raise awareness of how millions of pounds in donor aid is not reaching women, who make up the majority of the world's poor.
"What we're seeing is that millions of pounds are being poured into development projects, such as road infrastructure, that make life no better for the women who often don't own cars and don't have access to public transport," said Zohra Khan, gender policy officer at One World Action.
The organisation is calling on the UK Government to close the gap between its policy on funding gender inclusion in developing countries and the actual practice on the ground that has little impact on the lives of the women it is designed to help.
"We went out and did extensive research in countries that receive millions of pounds worth of aid money from the UK and EU, and tried to match the sound policy documents on poverty reduction with how it was actually being implemented," said Khan.
"We now need to work towards a fairer way of using and distributing this money that will benefit everyone."
One World Action hopes to gain the support of internal lobbyists at donor bodies such as the Department for International Development, and rally other international NGOs and development networks to support the campaign.