Diehard atheists may bristle at the mention of it, but Radio 4's Thought for Day remains a hallowed institution, a prized pulpit for religious broadcasting. There are currently three rabbis on its roster: that doyen of rabbinical broadcasters Lionel Blue, the Chief Rabbi Lord Sacks and the newest recruit, Rabbi Laura Janner-Klausner.

If the Reform movement has its way, we will be hearing a lot more of her. She has just been appointed its first "movement rabbi" to act as rabbinic spokesperson on religious affairs. It is a role that will see her travelling up and down the country speaking to Reform congregations, youth and other groups as well as offering what she says will be "a solid mainstream Jewish voice" to the nation at large.

As the daughter of Lord Janner, it is perhaps no great surprise to find her taking on a public role. But the Reform's new front woman grew up in a United Synagogue family whose members included her great uncle, the then Emeritus Chief Rabbi Sir Israel Brodie.

"When I was 12," she recalled, "we had a bat chayil at Norrice Lea [Hampstead Garden Suburb Synagogue]. It was a pivotal movement. It was on a Sunday and at least eight of us read. I read, in English, 'The Lord is My Shepherd, I Shall Not Want'. The next day I left."

Meanwhile, a friend had introduced her to the youth club at Alyth Gardens (North-Western Reform Synagogue) in Golders Green. "When I entered the synagogue, I saw men and women sitting together and I saw women leading tefilah and being completely involved. It really hit the spot. And so I shifted across to the Reform movement and, quite early, about the age of 13, I'd thought I'd really love to be a rabbi."

Talmud I adore and is the rooting for my Judaism

Her parents initially found her change of allegiance hard, concerned, she thinks, about how Sir Israel would take it. But when she told him of her youthful rabbinic ambitions, "He said to me, 'Lovely' – which was amazing. He did not have a heart attack. Maybe he didn't take me seriously."

But it took another 20-odd years before she entered the rabbinate. She went on gap year to Israel with the Reform youth movement - which cost just £120 in those days. Then, wanting to widen her horizons with the study of other faiths, she returned to read divinity at Cambridge, only to find the antiquated Christian-dominated course and dismissive comments about Judaism "pretty horrible". Outside tutorials, she threw herself into Jewish activities, commuting once a week to do youth work at Radlett and Bushey Reform Synagogue, to "rid myself of the toxicity of the divinity faculty".

After graduating, she went on aliyah at 22. She only has to mention Israel for you to feel the warmth in her voice - enthusiasm generally is her default setting, punctuated with expressive flourishes of the hands. One of her earliest memories is at the Western Wall with her parents at the age of four shortly after the Six Day War, and she has been "backward-and-forwarding" to the country ever since. "I'm personally responsible for global warming," she jokes.

She taught at Machon, the training institute for diaspora Zionist youth leaders, preferring history, politics and leadership skills to subjects such as the Holocaust and antisemitism. "Positive" Jewish values, motivate her, she says, rather than the "Oy vey, they're out to get us, therefore I must be Jewish" school.

Working also for another Jewish education institute, Melitz, she specialised in training tour guides and, after the Oslo peace accords, in promoting dialogue with Palestinians. "When the Palestinians I worked with heard I taught tour guides, they asked me to come to Bethlehem where they have a guiding school and teach guiding methodology," she said. One of the sites she took her Palestinians students to was the Museum of the Diaspora, showing "how you keep identity in diaspora".

It was in Israel that she met her husband David, now programming and planning director of the UJIA. "My auntie, Lady Morris of Kenwood, who is president of Habonim, introduced my parents," she said. "When she came to Israel one year, in 1986, she said, 'Laura, you've got to meet this fantastic guy." And so she introduced us. She has a very good track record. I really am a believer in shidduchim." Her "wonderful" husband and Israel's "amazing" childcare arrangements enabled her to work part-time, raise three, now teenage, children and acquire a couple of postgraduate degrees from the Hebrew University and Brandeis University in America. But after 15 years, in 1999, the family left for London as the political weather changed.

"I think if we had been living in Tel Aviv," she said, "we wouldn't have left. Jerusalem is such a difficult place to live because it is so ideologically intense."

Enrolled at Leo Baeck College in 2004, in her final year she began as a student rabbi at Alyth where she has been ever since. She is wearing "waterproof mascara", she says, because the thought of leaving congregational service is a wrench "beyond words".

Contrary to what some might think, she says she is "on the right" of the Reform spectrum and "pretty traditional" in her tastes - she helped to launch a monthly minyan at Alyth where the prayers are all in Hebrew.

"Talmud I absolutely adore and is the rooting for my Judaism," she says. "From my point of view, when Jewish decisions are made, it is through a halachic prism. Reform Judaism is mainstream and I believe has to be completely grounded in Progressive halachah and values and practice."

Her entrée into broadcasting came after a BBC executive heard her interviewed on a radio series about British Jews made by Jonathan Freedland, and recommended her to the head of religion on radio. Apart from Thought for the Day, she also appears on TV on BBC1's The Big Questions.

Her new position reflects the Reform movement's pitch for a higher public profile, although its leadership is at pains to discount the notion of it being some kind of alternative Chief Rabbi. It is not just about her, she stresses; she sees herself as an "enabler" who wants to make sure that other of her colleagues are "out there" speaking and publishing.

But she does acknowledge that the announcement is "interesting timing" when central Orthodoxy is about to embark on the search for a new Chief Rabbi and the United Synagogue is "in flux".

Now 47, she represents a new generation of rabbis in the public square. Her stance on Israel, combining deep attachment to it with concern about some of its policies - she chairs the British friends of Rabbis for Human Rights - will chime particularly with many younger British Jews.

She attacks the "blinkered thinking" that refuses to admit any criticism of Israel. But the "most frightening thing" is to hear Jews saying they do not want to know about it. "Bring me garinim [sunflower seeds] Friday nights and a good debate. For people who say they don't care, they are switching off, I believe if they switch off their Israel factor as part of their Judaism, it's impossible to hold together a creative, joyful, full Judaism."