The Women’s Equality Party says it would invest in “social infrastructure” with free childcare and “fully equal” parental leave.
The party, founded in 2015, is contesting seven seats on 8 June and launched its manifesto on Friday.
Leader Sophie Walker said it included plans for more parental leave and 40 hours free child care a week.
The Lib Dems are also pledging an extra month of paternity leave on top of the current statutory two weeks.
The party, which pushed for the introduction of shared parental leave when in coalition with the Conservatives, said it would outline how the measure would be funded when its manifesto is published.
But former Lib Dem minister Jo Swinson said: “More needs to be done in order to encourage men to take leave when they become a dad, to bond with their child during the early weeks and months of their life.”
Since 2003, new fathers have been entitled to two weeks’ paid leave if they meet certain criteria, such as having worked for their employer for a defined length of time. Statutory paternity pay is currently £140.98 a week or 90% of average weekly earnings, if that is lower.
In April 2015, new rights came in to allow parents to share up to 50 weeks of leave and 37 weeks of pay, if it is agreed with the employer with eight weeks’ notice.
Ms Walker told BBC Radio 4’s Women’s Hour that the party’s manifesto pledged a “fully equal” system of parental leave, for both parents, including adoptive parents and same sex couples. This would include three months off work on 90% of pay.
She said that many men could not currently afford to take their full paternity leave entitlement.
She put the cost of the policy at £6.5bn, based on average salaries, numbers of people with children and numbers of those in work and said it would be partly funded by taking £4bn from the government’s infrastructure investment fund. Employers would also be asked to pay an insurance levy of 0.076% of salary costs.
“We have to invest pound for pound in physical infrastructure and social infrastructure,” she told the programme.
“Physical infrastructure is one way of creating jobs and economic growth – but social infrastructure is really vital.”
She also elaborated on her plan for 40 hours a week free childcare for children aged between nine months and primary school age – at a cost of £33bn, which Ms Walker said should be funded by changes to pension tax relief, rises in alcohol and fuel duty and postponing cuts to corporation tax. She said the pledge would revolutionise lives and would help businesses.’
From September, three- and four-year-olds in England will be entitled to 30 free hours of care per week in term time – up from the current 15 hours, although there have been some concerns it will mean higher fees and extra charges.
Other pledges include tackling violence against women with better funding for specialist services, improving funding for social care and introduce a right to paid leave for carers.
Ms Walker said her party was inviting the biggest parties to steal its policies “because we want to get the job done”.
“The very DNA of this party is that we would like to put ourselves out of business, we also seek to work with like-minded people and this is very much part of that.”
Asked about criticism that the party risks splitting the vote and could unseat some women MPs, she said: “We sat down and worked out our election strategy based on ensuring that women’s representation in Parliament is maintained so we are not running anywhere where we would knock a woman out to the cost of the overall numbers.
“We have specifically also looked to make sure that we would not knock out a black, Asian or minority ethnic woman, because their representation in Parliament is even lower.”