Liberal Democrat leader Jo Swinson said her party will stop Brexit and “build a brighter future” as she set out her plan to become the next prime minister.

Ms Swinson, launching the Lib Dem General Election campaign in Westminster, said “change is possible” and credited her party’s “values” as the reason MPs from other parties have defected to hers.

She said she will “never stop fighting” for the United Kingdom as she vowed to “not let people wreck it”, and said people who say the Lib Dems cannot aim to be in government are “wrong”.

She ruled out propping up a Labour government if the General Election delivers another hung Parliament, insisting that she is offering a Lib Dem government and said this means “people need to vote Liberal Democrat”.

Ms Swinson told gathered supporters and media: “Our country needs us to be more ambitious right now.

“And we are rising to that challenge because this choice is about the future of our country for generations to come.”

She said she never thought she would be standing as a candidate for prime minister but added she is “absolutely certain” she would do a better job than Boris Johnson and Jeremy Corbyn.

Liberal Democrat leader Jo Swinson speaking at the launch (Steve Parsons/PA)

Ms Swinson said Mr Johnson is “modelling himself” on US president Donald Trump, while Mr Corbyn “will not give you a straight answer” on Brexit.

“We, Liberal Democrats, will stop Brexit,” she promised.

Asked how she would bring the country together if she plans to disregard the vote of millions of people in the 2016 referendum, Ms Swinson said: “As Liberal Democrats we are standing up for what we believe in, and being very honest and straightforward about that.”

She added: “There isn’t a Brexit that commands a majority. We want to stop Brexit and if we get a majority Liberal Democrat government that is exactly what we’ll do.”

Ms Swinson said staying in the EU would produce a £50 billion “Remain bonus” that could be spent on public services.

“Any type of Brexit will damage our economy, will cost jobs and starve our public services of the resources that they need.

“So we know that that Remain bonus will be £50 billion that we can spend on our public services, investing in our schools and in the welfare system to help the poorest in our society,” she said.

The party has said scrapping Brexit will generate billions for public finances because they say remaining in the European Union will mean the economy will grow faster than under Brexit, and will lead to higher GDP.

She said the election could be a moment of “seismic change” where a “new and different” politics could emerge.

Ms Swinson thanked Sky for proposing a TV debate between her, Mr Corbyn and Mr Johnson, after she vowed to take legal action if ITV does not change its format and include her in its planned head-to-head between the Labour leader and Tory leader.

Asked what her message to Mr Johnson and Mr Corbyn would be regarding TV debates, Ms Swinson said: “My message is I hope to see you there, or if not: what are you afraid of?”

She added: “I think it is ridiculous to suggest that the country is well served by a debate between two men who want to leave the European Union.”

Ms Swinson said she “cannot wait” to take on the two leaders, and on the issue of being left out of the ITV debate she added sexism is a “possible explanation”.

Asked about whether she would engage with Mr Trump if she was to become prime minister, Ms Swinson said that while she would not refuse to engage with the US president there is a “big difference between having a relationship and engaging, and rolling out the red carpet”, which is what she said the Tory Government has done.

Concluding her speech, Ms Swinson said: “Vote Liberal Democrat to stop Brexit and build a brighter future.”

Paul Scully, deputy chairman of the Conservative Party, said a vote for the Lib Dems “means either another failing, gridlocked Parliament or Jeremy Corbyn as Prime Minister”, adding: “Either way, that’s years more dither, delay and two more referendums.