London has regained its crown as the world's leading financial center, according to a survey of industry professionals on Wednesday, benefiting from the clear election victory by the Conservative party to overtake New York.The online survey of more than 2,000 individuals ranked 84 cities around the world in terms of the business environment, infrastructure, quality of workforce and financial sector development.London, which had top billing for seven years running in the twice-yearly survey, lost the top spot to New York last year.The shock election triumph by the Conservative party in the General Election in May helped it overtake New York this time, research company Z/Yen, which published the survey said.Ahead of the vote most polls had predicted a hung parliament, and a phase of political and economic instability.The result comes despite Europe's biggest bank HSBC and its Asia-focused rival Standard Chartered currently deciding whether to axe their London headquarters because of a government levy on bank profits and the uncertain outcome of an upcoming vote on Britain's membership of the European Union.London came top in every category, the report showed. Hong Kong, Singapore and Tokyo took third, fourth and fifth places respectively. Toronto, San Francisco and Washington DC were also named in the top 10.The only other European city to rank among the world's 10 leading financial centers was Zurich while Frankfurt was the European Union's second highest ranking city in 14th place.Chris Cummings, chief executive of lobby group TheCityUK, said a successful renegotiation of Britain's relationship with the currency bloc was "critical" to sustained growth of its financial industry, often described as the world's 'gateway' to Europe."London faces stiff challenges from other established centers, not just New York and the likes of Singapore, but also emerging centers in Asia, the Middle East and Africa. But it is the future of the UK's relationship with the EU which is arguably the most pressing issue," he said in a statement.Z/Yen's Mark Yeandle told newspaper CityAM that London's future status as the world's top financial center was also threatened by government efforts to control immigration."You can't have an international financial center without an international workforce," he told the newspaper.