LONDON — British Jews are furious about a new Jews for Jesus advertising campaign.

The advertisements, which hit Britain in July, show a group of fervently religious Jews at the Western Wall in Jerusalem. One of them is wearing a bright red Jews for Jesus T-shirt. The ad's slogan urges, "Think for Yourself."

The ads have appeared in two national newspapers and on four billboards in Jewish areas of London.

The Board of Deputies, the umbrella organization that represents most British Jews, has complained to the Advertising Standards Authority about the campaign.

"This advertisement is clearly based upon the principle that the majority of Jews are unable to 'think for themselves' — i.e., believe in Jesus," the board's director general, Neville Nagler, wrote in the complaint.

"This is a highly objectionable notion, and one that gives great offense to the vast majority of Jewish people in this country. We call for the immediate withdrawal of the advertisement," he wrote.

The Advertising Standards Authority has opened an investigation into the campaign after receiving nearly 20 complaints, a spokeswoman said.

The authority has compiled a report summarizing the complaints and requested a response from Jews for Jesus, whose headquarters is based in San Francisco.

The regulators expect to rule on the case by the end of August and could order the missionary organization to take the billboards down.

Joseph Steinberg, the U.K. director of Jews for Jesus, said the idea for the billboard — which features him in the Jews for Jesus T-shirt — came from a similar campaign used in the United States a few years ago.

He said the current advertising campaign was part of an international missionary drive being spearheaded this summer.

"We are now in a very large outreach worldwide. London is a place where we have been very proactive," he said.

The group has been active in Britain for 13 years, he said, and currently has a paid staff of nine, as well as volunteers.

A sizeable proportion of the people behind Jews for Jesus are not actually Jews, but Christians.

Steinberg said the ads were supposed to be funny.

"It was done tongue in cheek," he said. "The only thing I can think is that Jews are offended by the message, which is that you can be Jewish and believe in Jesus."

But Rabbi Shmuel Arkush, head of the U.K. anti-missionary group Operation Judaism, said there are several reasons Jews are upset.

For starters, he said, the implication that fervently religious Jews do not "think for themselves" is outrageous.

"These are people who would be spending hours a day studying the Torah. The inference that [Jews for Jesus] think and we don't is such an affront," he said. "It's absolute chutzpah, and that's what riles people — and they're entitled to be riled."

In addition to the slogan, Arkush said, the missionary movement is problematic.

"Let's call a spade a spade: You have a group of publicity-seeking individuals who are trying to peddle the impossible," he said.

For a Jew to believe in Jesus is "theologically without foundation. You have Jews, and you have Christians. You can't dance at both weddings."

There are a whole raft of registered charities that specialize in targeting Jews for conversion, he said.

"That puts a wedge between faith groups. We need religious authorities to promote respect between religions," he argued.

And he rejected Steinberg's argument that Jews who were upset had missed the joke.

"If he considers this to be amusing," Arkush said, "then I hope he has another job.''