The Labour leadership race will explode into life on Saturday as the first regional hustings take place.
Early front-runner Sir Keir Starmer and self-styled left-wing candidate Rebecca Long-Bailey are among those seeking support to take over from Jeremy Corbyn as party leader.
Mrs Long-Bailey and shadow foreign secretary Emily Thornberry officially launched their campaigns to lead Labour on Friday night.
Backbenchers Jess Phillips and Lisa Nandy are also in the race to succeed Mr Corbyn in the ballot that will be decided in early April.
Setting out her stall in her hometown of Guildford, Ms Thornberry warned that Labour faces “a long, tough road back to power” after the party suffered its worst general election defeat since 1935.
The Islington South and Finsbury MP, who narrowly secured the necessary support from MPs to enter the race on Monday, insisted she was the best placed to oust Prime Minister Boris Johnson within five years.
She told the PA news agency: “Boris Johnson has all sorts of problems with women.
“And he is going to have an even bigger one if I become leader of the Labour Party.
“I think that he has a problem with women.
“I have spoken to a number of women who have said that the way he deals with them – and they are younger women – is that he flirts with them.
“He makes light of them and he undermines them. He has problems with women such as myself. He doesn’t know what to do with me.
“I think that he doesn’t know how to relate to women.”
She added: “I think that a competent alternative government could get back into power within five years.”
Shadow business secretary Ms Long-Bailey kicked off her campaign with a speech in Manchester, in which she said her party did not talk enough about “aspiration”.
She also vowed to “shake up” the way government works, and put power into the hands of voters.
Described as a “continuity Corbyn” candidate said to be favoured by the current leadership and backed by campaign group Momentum, her supporters have bridled at the description.
As she took to the stage at the Museum of Science and Industry, some of the 300 or so supporters at the event broke into a chant of “Oh Jeremy Corbyn”.
Mrs Long-Bailey told them: “Hey guys, we’re going to have to think of a new song you know. No pressure.”
She was asked why Labour had failed with voters, returning their worst electoral result since 1935.
Mrs Long-Bailey said: “I think for me we had some fantastic policies, I know because I helped write some of them, and really the message didn’t resonate with our voters.
“And what we should have been talking about is aspiration.
“Because everything we are trying to build and I am going to try to build as leader of the Labour Party is about realising the potential, truly realising that quality of life increase, whether you are a business, whether you are an industry or an individual, our role as a party is to improve your living standards and the wealth you can accumulate as communities.
“And we didn’t say that. We didn’t match that with a message of aspiration.
“We want an economy where everyone does well.”
All five candidates will appear at the event on Saturday to mark the start of their hustings tour around the UK.
Events are planned in cities including Durham, Bristol, Cardiff, Nottingham, Glasgow and London, as well as in the West Midlands and Bedford.
The result of the contest will be announced on April 4.