Fitch Ratings, a London-based international credit rating agency, Thursday said that it would review Britain's sovereign credit rating if Scotland votes 'yes' on independent referendum. The credit rating company expects a 'no' vote in September's referendum on Scottish independence. However, "The implication of a possible 'yes' vote for the residual United Kingdom (England, Wales and Northern Ireland) still merit closer analysis given there would be additional, albeit moderate risks" for the country's public debt, external finances, currency arrangement and banking sector, said Fitch in a report. "As we have previously emphasized, the UK's gross debt ratio will need to be lower than its current level and steadily declining before any upgrade back to 'AAA', a prospect that would be delayed by such a debt shock," warns Fitch. Fitch affirms Britain's AA+ sovereign credit rating, with a Stable outlook last December. Financial institutions like Standard Life and Royal Bank of Scotland have warned that they are poised to move headquarters if Scotland votes to be independent. The Scotland's independent referendum will be held on Sept. 18, 2014.