LONDON — As Britain prepares to vote on June 23 on whether to remain in the European Union, skepticism about the bloc is on the rise across Europe, with about two-thirds of Britons wanting some powers returned to their national government, according to an opinion poll released on Tuesday by the Pew Research Center, a nonpartisan institution based in Washington.

The survey of respondents in 10 European countries showed increasing dissatisfaction with the European Union since last year, a period of low growth and during a migrant crisis, particularly in France and Spain.

In France, 38 percent of respondents viewed the European Union favorably and 61 percent viewed it unfavorably. In Greece, 27 percent viewed it favorably and 71 percent unfavorably.

In Britain, by contrast, 44 percent of respondents viewed the bloc favorably while 48 percent viewed it unfavorably.