Intermarriage between Jews and non-Jews in the UK has risen to 26 percent, but is still only half the level seen in the United States, a new report shows.

Work by the Institute for Jewish Policy Research (JPR), published on Wednesday, found that the increase reflects an “upward trend” but shows that it has “risen only two percentage points since the 1990s”.

It found that only three in ten children brought up by intermarried parents were raised as Jewish, with the child’s identity dependent to a large extent on whether the mother is Jewish.

“Up to 36,711 Jews have non-Jewish partners,” said author Dr David Graham, a senior research fellow at JPR. “Intermarried Jewish men are four times less likely to raise Jewish children than intermarried Jewish women.”

Graham said that, even if the child is brought up Jewish, his/her parents’ differing ethnicities “at least doubles” the chance of the child intermarrying. He added that in a mixed marriage, the Jewish partner is far less likely to maintain Jewish customs and tradition.

“Intermarried Jews exhibit far weaker levels of Jewish practice and performance than in-married Jews,” he said. “For example, 91 percent of in-married Jews light candles on Friday night at least occasionally, compared with 36 percent of intermarried Jews.”

Religious figures said the report failed to explain why the rate of intermarriage was increasing, and suggested that this was a result of social shunning.

“The JPR report finds that intermarried couples are less likely to bring their children up as Jewish, but it doesn’t tell us why,” said Rabbi Aaron Goldstein, Senior Rabbi Northwood and Pinner Liberal Synagogue.

“Surely, the figures say as much about how the Jewish community treats such couples as it does about the attitudes of the couples themselves? If we treat people with distain then it is hardly surprising that they choose to opt out.”

Graham acknowledged communal leaders’ longstanding preoccupation with Jews “marrying out,” saying: “While the marriage of Jews to non-Jews remains central to Jewish anxiety about the future perpetuation of the community, there is more to Jewish partnership formation than intermarriage.”

The report, based on data from the National Jewish Community Survey and the 2001 and 2011 National Censuses, also showed a large increase in the number of couples co-habiting over recent years, but with less than two percent in same-sex relationships.