Jo Swinson has closed the Liberal Democrat conference with a message that the next election would be a fight for the “heart and soul of Britain” as she pledged to stop Brexit and counter the rising tide of populism and nationalism.

Announcing to rapturous applause that she was appearing before delegates “as your candidate for prime minister” Swinson used her first conference speech as leader to renew attacks on Boris Johnson and Jeremy Corbyn. She said the country now needed the Lib Dems to give voters a better choice.

Her address contained no new policy announcements but instead reiterated pledges made on previous days, notably that a Lib Dem majority government would stop the Brexit process without resorting to a second referendum.

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Her speech was also noticeably devoid of onerous references to the party’s backing for a second referendum. Instead she focused on the Lib Dems’ plan for a snap election – where in the case of a majority result, they would revoke article 50 – which has been divisive among some members.

She also pledged to base future budgets not just on GDP figures but on factors of national wellbeing, inspired by a model used by the the prime minister of New Zealand, Jacinda Ardern. Policies would be developed by gauging their long-term impact on life satisfaction, happiness, anxiety and the feeling of whether something had been worthwhile. A similar proposal was made by Labour in June.

There were promises to a set a target of net zero carbon emissions by 2045, create a new Green Investment Bank and tackle youth crime with a public health-based approach.

Swinson’s supporters said it was a speech intended to give members a broad brush idea of her vision for Britain, the EU and the party, and was not intended to be policy-heavy.

At the next general election she said the country deserved “a better choice than an entitled Etonian or a 1970s socialist”, referring to the Conservative and Labour leaders respectively.

“Ahead of us we have the fight of our lives for the heart and soul of Britain. The next few weeks are about deciding what kind of country we are, and who we want to be. Whether we tackle our biggest challenges with our closest allies, or on our own; whether we welcome those who want to build a better life in our country, or shut the door on them; whether we ensure every single child can go on and fulfil their dreams.”

On Brexit, Swinson pledged to revoke article 50 and thus stop Brexit “on day one” as prime minister, “because there is no Brexit that will be good for our country”.

Profile Jo Swinson Show Hide Jo Swinson, the new Liberal Democrat leader, is something of a veteran in the party, even in parliament, despite not turning 40 before next year. The party’s deputy leader and foreign affairs spokeswoman was just 25 when, in 2005, she took her home seat of East Dunbartonshire, becoming not just the “baby of the house” – the unofficial title for the youngest MP – but also the first Westminster representative born in the 1980s. She served as a junior minister in the coalition government and was a prominent party member until she – along with many other Lib Dems – lost her seat after the party’s near-wipeout in the 2015 general election. She returned in 2017’s snap election and has become one of the party’s most visible figures, long considered the natural heir to Vince Cable. Swinson has been vocal on a number of issues, including the Lib Dems’ record in coalition with the Conservatives. In September she said the party must “own the failures” of the coalition, citing the “hostile environment”, the bedroom tax and NHS changes as policies she particularly regretted. Swinson said the party had been complicit in inflicting too high a price on the poorest to cut the deficit. “I’m proud of what we achieved, but I’m not naive or blinkered about it,” she told the Lib Dem conference. “If we are to claim the successes of our time in government, we need to own the failures of it too. We lost too many arguments. When they fought dirty, we were too nice.” She has also pushed for a strongly anti-Brexit stance, which helped the Lib Dems reach their best poll ratings since 2010. In announcing her leadership bid Swinson called on remain voters from other parties to make the Lib Dems their permanent home. At the start of the 2019 general election campaign she ruled out doing any deal with Labour which would put Jeremy Corbyn into Downing Street. A mother of two young children, Swinson was inadvertently at the centre of a row last year when it emerged the Conservatives had broken a “pairing” agreement with her while she was on maternity leave to try to swing a crucial Brexit vote. The backlash helped push forward new plans for proxy voting by MPs. Peter Walker Political correspondent Photograph: Graeme Robertson

Another standing ovation was received at the finale of the speech when she said: “We can change our politics, stop Brexit and win a brighter future.”

She condemned Johnson’s push towards a no-deal departure, saying it would devastate the economy.

“This Brexiteer government wants to pay for their ideology with other people’s jobs. The truth is, they won’t be affected, and they won’t be there to help when the redundancy notices are handed out.

“They won’t be there when the homes are repossessed or when the marriages break down under the financial stress. Which makes what Boris Johnson is doing quite so sickening – he knows all of this.”

She criticised Corbyn, saying: “Nigel Farage might be Brexit by name, but it is very clear that Jeremy Corbyn is Brexit by nature.”

“If he had campaigned to remain in 2016 with half of the energy he had put into the 2017 election, we may have seen a different result.”

As the first woman to lead the Lib Dems, she received one of the warmest rounds of applause and cheers from members when she lambasted the prime minister’s language.

“Boris Johnson’s insults of choice are rather revealing. Big girl’s blouse, girly swot. If he thinks being a woman is somehow a weakness, he’s about to find out: it is not,” she said.

She ended her speech with: “At the next general election, voters will choose the kind of country we want to be: insular, closed and selfish; or collaborative, open and generous.

“We can defeat nationalism and populism. We can change our politics, stop Brexit and win a brighter future.”

She spoke with ease for her debut conference speech, appearing to have memorised most of her 45-minute address and eschewing the traditional lectern.

The 1997 Spice Girls track Spice Up Your Life was chosen as the backing track for her walk offstage to meet her husband Duncan Hames – a former Lib Dem MP – and her mother, Annette.