Boris Johnson is promising a fast track "NHS visa" making it easier for overseas doctors and nurses to work in the UK if the Tories win the General Election.
Ministers said the scheme would enable the health service to continue to attract the finest medical staff after Britain has left the EU.
However, Labour accused the Tories of "tying themselves in knots" – using "dog whistle anti-immigrant rhetoric" while trying to bring in migrant workers to keep public services working.
Labour was focusing its campaign effort on measures to support women in the workplace, including raising statutory maternity pay and better entitlement to flexible working.
The Conservatives' new NHS visa will ultimately form part of the party's planned points-based immigration system to be introduced after Brexit.
The move reflects concern within the health service that it will struggle to attract the staff it needs when Britain is outside the EU.
Under the scheme, the cost of a visa for health professionals would be halved from £928 to £464, while applicants would be guaranteed a decision within two weeks.
Applicants coming to work in the NHS would receive preferential treatment with extra points under the points-based system, and no cap on numbers entering through the NHS route.
They would also be able to pay back the cost of the immigration health surcharge through their salary if the charge is not already covered by the NHS trust offering the job.
The Tories have already announced a fast-track visa route to attract specialists in science, engineering and technology.
Home Secretary Priti Patel said an Australian-style points-based system would allow Britain to control the numbers coming into the country while remaining open to essential professions such as nursing.
"That means the best of both worlds – attracting talent from around the world so our NHS continues to provide brilliant service while ensuring that it isn't put under strain by opening Britain's borders to the entire world," she said.
However shadow home secretary Diane Abbott said the Tories were "tying themselves in knots" over immigration.
"They use dog whistle anti-migrant rhetoric but are forced to accept we need migrant workers for key sectors, not just the NHS, but many more besides," she said.
Liberal Democrat home affairs spokeswoman Christine Jardine said the visa fees amounted to a "nurse tax" on staff from the EU who could currently come to Britain for free.
"The Conservatives have effectively created a new nurse tax. It is an insult to the thousands of people who dedicate their lives coming to work for our health service from the EU," she said.
Meanwhile Labour was focusing on its plans to bring about a "step change" in the way women are treated at work.
Shadow women and equalities minister Dawn Butler said a Labour government would increase statutory maternity pay from nine to 12 months, improve entitlement to flexible working and take further steps to tackle sexual harassment.
"Labour will deliver a workplace revolution to bring about a step-change in how women are treated at work," she said.
But the Tories warned that the measures would simply result in lost jobs.
After a tumultuous start to the campaign both the main parties saw further candidates forced to stand down over controversial past remarks.
Ex-BBC Radio Norfolk presenter Nick Conrad quit as Tory candidate for Broadland after heavy criticism of comments he made in 2014 during a discussion about a high-profile rape case, saying women should "keep your knickers on".
Labour's candidate for Aberdeen Kate Ramsden stood down over a social media post – highlighted by The Jewish Chronicle – likening Israel to "an abused child who becomes an abusive adult".
She apologised unreservedly saying she could see that "many Jewish people had been hurt by my words".
A Labour source said the party had taken "swift and robust action" after extra due diligence checks had uncovered material of concern.
Labour's candidate for Edinburgh South, Frances Hoole, was also dropped after the party refused to endorse her following a social media attack on her SNP opponent, Joanna Cherry.