LONDON, ENGLAND - The 19th century founders of British investment bank Rothschild and top law firm Freshfields engaged in business linked to the slave trade, the Financial Times reported on Saturday, citing new research.

The news could prove contentious in the United States, where both firms operate and where numerous banks and other bodies have been pressured to make amends for profiting from slavery, the newspaper said.

Documents from Britain's national archives showed that Nathan Mayer Rothschild had allowed the use of slaves as collateral in banking dealings with a slave owner, while Freshfields' founding partner James William Freshfield acted as a trustee in deals involving Caribbean slave plantations, the FT reported. Freshfields said it had not been aware of the documents, which academics at University College London are studying.

"James William Freshfield himself was an active member of the Church Missionary Society ... (which) was committed to the abolition of slavery," a spokesman said.

Rothschild himself was later involved in helping the British government raise finance to compensate slave owners when it abolished slavery in its colonies in the 1830s, the FT said.

A Rothschild spokesman was not immediately available for comment.

But the FT quoted a spokesman as saying: "These allegations appear inconsistent and misrepresent the ethos of the man and his business."