France’s opposition Socialist party yesterday urged President Nicolas Sarkozy to pressure US authorities to ensure Dominique Strauss-Kahn is given a fair chance to defend himself on sex assault charges.

Socialist Party spokesman Harlem Desir appeared to suggest Mr Sarkozy should urge New York judges to free the former IMF chief on bail “so that Dominique Strauss-Kahn can organise his defence in a decent fashion”.

Mr Desir noted that Mr Sarkozy had previously intervened in the case of “other French people caught up in judicial matters abroad... We do it when it concerns one of our compatriots in Mexico or in other countries”.

This appeared to be a reference to Florence Cassez, a Frenchwoman arrested in Mexico in 2005 along with her boyfriend, an alleged gangleader, and jailed for 60 years for kidnapping, organised crime and weapons possession.

French officials believe there were shortcomings in her trial and Mr Sarkozy has urged his Mexican counterpart Felipe Calderon to allow her to come home, without success, provoking a diplomatic row. Mr Strauss-Kahn, a leading Socialist and former finance minister was expected to run against Mr Sarkozy in next year’s presidential election. Mr Desir said Mr Sarkozy’s intervention should show “respect for the judicial institutions of the United States” but complained: “I really can’t understand why it was felt absolutely necessary he remain in detention.”