Theresa May is promising a new deal for workers in her latest push to win over Labour voters.
The Prime Minister will offer a package of extra rights and promise further increases in the national living wage if she is returned to Downing Street.
Meanwhile Jeremy Corbyn will promise an extra £37 billion for the NHS and Tim Farron will vow to boost public sector pay as they each address the Royal College of Nursing's conference in Liverpool.
The two leaders will appear at the RCN conference after the union announced plans for a summer of protests following a poll of its members showing strong support for strikes over pay.
The RCN warned, unless the next government drops the 1% cap on pay rises, it will hold a ballot on industrial action later this year, threatening the first ever strikes by its members.
At the start of a week which will see the main parties publish their manifestos, the Prime Minister will promise to extend protections for workers in the so-called "gig economy", such as drivers for Uber and internet delivery firms.
She will also offer new statutory rights to leave for workers who need to care for a family member or following the death of a child.
Workers will also be given representation on company boards and a new statutory right to information about takeovers, asset disposals and major reorganisations involving their firms.
The package includes a commitment to further increases in the national living wage and measures to protect workers' pensions in the wake of the BHS scandal.
Mrs May will claim the package amounts to the "greatest expansion in workers' rights by any Conservative government in history" and would help ensure the proceeds of economic growth "are spread to everyone in our country".
Labour leader Mr Corbyn will use his RCN speech to offer a major cash boost to the NHS and deliver a warning about the health service's future if Mrs May remains in power after June 8.
He will blame the Tories for leaving the NHS vulnerable to the ransomware cyberattack and warn another five years of Conservative rule would result in the health service being "broken up and plundered" by private firms.
"You can't trust the Tories with our NHS. Labour founded the NHS and we will restore it to good health," he will say.
Liberal Democrat leader Tim Farron will tell the conference in Liverpool that his party would scrap the 1% public sector pay cap, something Labour has also committed to.
Ahead of his appearance Mr Farron said: "Nurses have been treated like dirt by the Conservatives for far too long.
"They are working more hours, for less pay and with higher levels of stress, meaning more pressure on the NHS and worse outcomes for patients.
"Theresa May doesn't seem to care that the system is underfunded and heading towards collapse.
"The Liberal Democrats will fix the chronic underfunding facing the NHS and give nurses the pay rise they deserve."
Under new plans to be unveiled in their upcoming manifesto, the Lib Dems said the end to pay restraint would result in an average pay rise of £779 for staff.
RCN general secretary Janet Davies said: "The NHS does not need irresponsible politicians, of any party, offering 'cheques in the post'.
"The bus slogans and sticking plasters let patients down and they must avoid the temptation.
"Party leaders must put patients before politics by committing to the hard cash and staff the NHS needs.
"After the election, for the sake of patient safety, the Government must scrap the cap on nurses' pay and help to fill the 40,000 vacant jobs."
Mr Corbyn's promise of extra cash came as a poll indicated the NHS, rather than Brexit, is now the most important issue to the public.
The Survation poll for ITV's Good Morning Britain found 17% said the NHS was their top priority, ahead of Brexit on 12%, previous work by the pollster put Brexit on 15% and the NHS on 14%.
The survey also revealed widespread support for the policies contained in Labour's leaked draft manifesto, but not for Mr Corbyn's party.
More than 50% of those surveyed supported measures including a tax hike for people earning more than £80,000, the abolition of tuition fees, building extra council houses, renationalising the railways and setting up publicly-owned energy firms.
But of those who stated a voting intention, 48% would vote Conservative, up one point since the last poll earlier this month, while Labour was unchanged on 30% with the Lib Dems up one point on 8% and Ukip unchanged on 4%.
:: Survation interviewed 1,016 British adults by telephone between May 12 and 13.