Jubilee Debt Campaign activists held up a washing line outside the Hilton London Tower Bridge hotel in Tooley Street as delegates arrived for a global trade summit.
The campaigners, dressed as French maids, gathered on Tuesday morning to demand that governments to "clean up their exports".
"Lax international trading standards mean government export credit agencies across the world are using public money to back private business deals which fuel human rights abuses, environmental destruction, corruption and poverty," claims the campaign.
"The UK's export credit agency, the ECGD, operates under a cloak of secrecy, participating in a global race to the bottom on ethics and using taxpayers' money to back business deals which have racked up billions of pounds in Third World Debt."
Speakers at the three-day ExCred-21 convention include David Craig, manager of ECGD Project and Structured Finance.
The Jubilee Debt Campaign is the UK coalition campaigning for cancellation of unjust and unpayable poor country debts.