Many Israelis were disappointed when Rabbi David Stav failed to win election as the country's Ashkenazi Chief Rabbi last year. There had been high hopes of him prising the institution from its Charedi grip and introducing a more modern Orthodox outlook.

The 55-year old municipal rabbi of Shoham, in central Israel, was co-founder some 20 years ago of Tzohar, a group of rabbis who have sought to reach out to secular Israelis alienated by what they see as a coercive religious establishment.

But Rabbi Stav - who recently visited the UK as guest of the Israeli education organisation Lavi Olami - said, "We don't have time to be disappointed. We are committed to bringing the changes we promised to Israeli society."

One change came into effect earlier this month. Tzohar, working with the Israeli Bar Association, has launched a new voluntary prenuptial agreement for couples, which is designed to stop partners blackmailing each other in the event of divorce.

Since there is neither civil nor recognised non-Orthodox marriage in Israel, marriage regulations are governed by traditional halachah. If a man refuses to give his wife a get, she can become trapped as an agunah, a chained woman, unable to remarry. Some men will try to force an unreasonable financial settlement on their wives in return for a get, while a few even go to jail rather than give one at all.

Halachically, converting kids is easier. This could be a solution to the crisis in Israel

The basis of the PNA, Rabbi Stav explained, is that spouses pledge to provide their partner with a certain sum of mezonot (food). As long as they live together, they don't demand it. But once they split up, they can demand that the pledge is honoured. "And since we believe most people would not want to give away half of their salary to their spouse, we believe it will encourage them to give a get as soon as possible."

With one in three Israeli Jewish marriages ending in divorce, he said "we will recommend every couple getting married to sign this agreement".

Tzohar rabbis also help couples to marry. "We have 700,000 immigrants who have arrived from Russia after 1990 and maintain they are halachically Jewish. But when they come to get married, they have no proof that they are Jewish." Tzohar has opened half a dozen branches in Israel and three in the former USSR to find evidence of the couple's Jewish origins. They have even trawled old KGB archives. "And not only Russians - we have helped Americans, Canadians, Argentinians, Mexicans."

Then there are the estimated 400,000 Israeli Russians who are not halachically Jewish yet mix within Israeli Jewish society. According to the rabbinate, they remain ineligible for Jewish marriage. "We will be the only country in the world that prevents its citizens from getting married in their own country," Rabbi Stav said. "It is something that is not feasible."

But if Israel allowed them to marry civilly, he feared, it would pave the way for "huge intermarriage".

Yet there could be a way forward. Israel's government recently approved a move to give local town rabbis the freedom to conduct conversions, which until now have been confined to the few rabbinic courts appointed by the chief rabbinate.

Although most of the non-halachic Russians "are not observant, there is a halachic way to convert at least their kids, and to encourage them to go to observant schools that teach Yiddishkeit," Rabbi Stav said. "Halachically, the process for converting kids is easier. The fact that they will learn in observant schools will guarantee the sincerity and seriousness of the intention of these kids to be part of observant society. This could be a solution for the conversion crisis."

However, the chief rabbinate has refused to play ball and will not permit the conversion of the children - "that's what the struggle is about", he said. While Tzohar backs the new municipal rabbinic courts, the chief rabbinate has threatened to withhold recognition of conversions performed in them.

Only recently he suggested Israel's internal divisions could pose more of a threat than an Iranian nuclear bomb. But although anger at the religious establishment may be growing and fuelling resentment against Judaism, he also detects a contrary trend among secular Israelis of "a real spiritual thirst".

Around 10 years ago Tzohar started educational Yom Kippur services for secular Israelis, in community or cultural centres rather than synagogues, which might be offputting for them. The innovation proved so successful that Tzohar now runs services in 350 locations every year.

On Purim, Tzohar also held megillah readings in 250 venues and three years ago started Tikkun Leil gatherings where secular Israelis could study Torah all night on Shavuot. It's a model he believes could be exported elsewhere.

While in London, he discussed with Chief Rabbi Ephraim Mirvis the idea of providing similar services for expat Israelis here. "We have a huge population of Israelis in London who are not connected to synagogues," he said. "We ought to make all efforts to engage them, so they will not get lost. I hope in six months we will have a joint project for Yom Kippur."