Francois Hollande, tipped to become France's next president, pushed his call for more financial markets regulation during a visit to woo French voters in London on Wednesday.
But in Europe's financial hub, the Socialist tried to play down concerns about his intention to crack down on the financial world if he comes to office, telling one journalist: "I am not dangerous."
Hollande held talks with Ed Miliband, leader of Britain's opposition centre-left Labour party, and made a speech at a university.
The presidential frontrunner played down the lack of a meeting with Prime Minister David Cameron, who this month wished conservative French President Nicolas Sarkozy luck in the campaign, describing him as a "friend".
Hollande said he had not asked for a meeting with Cameron. "Today I felt that my priority was meeting my friends from the Labour Party," he said.
"The day might come, and it might be soon, if I manage to convince the French voters on May 6, when I will have to meet Mr Cameron."
A Downing Street spokeswoman said: "The president is the prime minister's opposite number and it would not be usual for the prime minister to meet with opposition candidates while an election campaign is underway."
Hollande's manifesto pledge to renegotiate an EU fiscal treaty, and his description of the financial world as his "adversary" at a recent campaign rally, have ruffled feathers in the City of London financial district.
In London, he said "we need more regulation everywhere".
At a joint press conference after their talks, Miliband said he was "very, very impressed by the lead Francois Hollande has shown" on the issue of getting tough on financial regulation.
"We need to reform the way that finance works and to reform the way that capitalism works. He is absolutely right," Miliband said.
Hollande was also reaching out to French people living in Britain -- the 300,000-strong community in London alone makes it by some estimates France's sixth biggest city.
As well as voting in the two-round presidential election in April and May, the 80,000 French voters living in Britain will, for the first time, elect their own representatives in France's National Assembly in June.
A new constituency for northern Europe covers 10 countries, but the majority of the voters live in London.