In diplomacy, either "Madam Ambassador" and "Ambassador (lastname)" is an appropriate formal mode of address for a female ambassador. In some countries, the wife of an ambassador also may be referred to as "Madam Ambassador". This is the case in French-speaking countries, but not among U.S. diplomats or the foreign diplomatic corps in Washington. In countries where the wives of ambassadors may also be titled "Madam Ambassador", the Foreign Service Institute advises U.S. diplomats to "refer to a female ambassador by her last name (Ambassador Jones) to avoid confusion and ensure that she receives her due respect." "Madam High Commissioner" is an appropriate formal mode of spoken address for a female high commissioner. The title "Madam" may also be used to address female "chargés d'affaires" although titles "Mrs." or "Ms." may be used instead.