Sir Keir Starmer said his views on gender issues 'start with biology' despite previously stating that a women could have a penis.
The Labour leader said he backed blocking trans women from female-only hospital wards and prisons following the Government's proposed changes to the NHS constitution.
The changes will see trans women banned from female-only wards and also give female patients the right to request to be treated by a doctor of the same sex for intimate care.
Speaking on ITV's Good Morning Britain about the proposed changes, Sir Keir said: 'There's a distinction between sex and gender. The Labour Party has championed women's rights for a very long time.'
The Labour leader has repeatedly faced questions about his views on transgender issues.
He has previously said that '99.9% of women' do not have a penis and in 2021 he said it was 'not right' for Labour MP Rosie Duffield to state that 'only women have a cervix'.
Sir Keir Starmer has said his views on gender issues 'start with biology' despite previously saying he thought women could have a penis
The Labour leader appeared on Good Morning Britain on Tuesday following the Government's proposed changes to the NHS constitution
But asked about his response to Ms Duffield, Sir Keir said: 'Biologically, she of course is right about that.'
Asked if he would apologise to the Canterbury MP, Labour leader Sir Keir Starmer said: 'I don't want this to go back into this toxic place where everybody is divided.'
But he said: 'Rosie Duffield and I get on very well, we discuss a number of issues.
'She's a much-respected member of the Parliamentary Labour Party and I want to have a discussion with her and anybody else about how we go forward in a positive way.'
Asked how Labour would respond to transgender women who did not want to go on to male hospital wards, Sir Keir said: 'We have to accommodate that situation as it arises, but treat everybody with respect and dignity. I do not accept this is an issue that cannot be resolved with respect and dignity.'
He added: 'Where we need to make accommodations, we can make accommodations.
'As a country, we're a pretty reasonable, tolerant bunch and most people know that there are a small number of individuals who do not identify with the gender that they were born into.
'Many of them suffer great distress and trauma. And for my part, I'm perfectly happy to say I would treat them, as I would treat anybody, with respect.'
Labour leader Keir Starmer and Labour deputy leader Angela Rayner join people taking part in the annual Pride Parade in the streets of Soho in London on July 2, 2022
Labour MP Rosie Duffield who previously stated that 'only women have a cervix' on 2021. Keir Starmer later criticised her comments saying they were 'not right'
Under the planned revisions to the health service's constitution, transgender people could be placed in a room on their own if another patient requests to be in a single-sex ward.
This would be permitted under the Equality Act 2010 when appropriate, 'such as respecting a patient's wish to be in a single-sex ward', according to the Department of Health and Social Care.
In October, former health secretary Steve Barclay said he would look into changing the constitution to address concerns about trans women using wards intended for biologically female patients.
Discussing the changes, Health and Social Care Secretary Victoria Atkins said: 'We want to make it abundantly clear that if a patient wants same-sex care they should have access to it wherever reasonably possible.
'We have always been clear that sex matters and our services should respect that.
'By putting this in the NHS Constitution we're highlighting the importance of balancing the rights and needs of all patients to make a healthcare system that is faster, simpler and fairer for all.'
Maya Forstater, chief executive of Sex Matters, a human rights charity that campaigns for clarity on sex in law, policy and language, said: 'Victoria Atkins explicitly referring to biological sex is very significant.
'It will benefit anyone who needs same-sex intimate care in the NHS in England, or who may do so in the future.
'We can expect an outraged response from trans rights activists, but this is simply a return to common sense, and an overdue recognition that women's wellbeing and safety matter.'
Health and Social Care Secretary Victoria Atkins (pictured) said that 'if a patient wants same-sex care they should have access to it wherever reasonably possible'
Maya Forstater (pictured), chief executive of Sex Matters, said: 'Victoria Atkins explicitly referring to biological sex is very significant'
The new document will also aim to ensure different biological needs are met, and that illnesses and conditions that impact men and women in different ways are communicated clearly to patients.
Health minister Maria Caulfield said: 'Updating the NHS Constitution is crucial to ensuring the principles underpinning our NHS work for everyone.
'This is about putting patients first, giving them the dignity and respect that they deserve when they are at their most vulnerable.'
However, shadow health secretary Wes Streeting said 'rights on paper are worthless unless they are delivered in practice'.
'The NHS Constitution already pledges that no patient will have to share an overnight ward with patients of the opposite sex, but that is not the case for too many patients,' he added.
'Labour supports single-sex wards and will provide the staff, investment and reform the NHS needs to make sure every patient can be cared for safely.'
Professor Nicola Ranger, chief nursing officer and deputy chief executive of the Royal College of Nursing (RCN), said: 'Patients are already able to request intimate care from a staff member of the same sex, but in an NHS missing tens of thousands of nursing staff it is nigh-on impossible to accommodate with any consistency.
'It's also important to recognise that nursing staff treat all patients with the utmost respect and professionalism, no matter their gender.
'Trans and non-binary patients are deserving of high-quality care like any other patient and changes to health policy should be done with them, not unto them.'
Dr Emma Runswick, deputy chairwoman of the British Medical Association (BMA) council, warned some changes 'run the risk of causing more harm than good - with the potential to incite further discrimination, harassment and ostracisation of an already marginalised group'.
'If these proposed changes come into effect, transgender and non-binary patients will potentially find their access to vital NHS services limited,' she added.
Changes to the NHS 's constitution proposed by ministers will give women the right to request to be treated by a doctor of the same sex for intimate care (Stock photo)
Shadow health secretary Wes Streeting said, regarding the proposed changes, that 'rights on paper are worthless unless they are delivered in practice'
The NHS Constitution outlines the rights of patients and staff and is updated every 10 years.
Other proposed changes, which are subject to an eight-week consultation, include committing to providing families with a second opinion when a patient's condition is deteriorating.
The rollout of the escalation process, also known as Martha's Rule, started earlier this month and follows the death of 13-year-old Martha Mills in 2021.
She developed sepsis after suffering a pancreatic injury following a fall from her bike.
Martha's parents, Merope Mills and Paul Laity, raised concerns about their daughter's health a number of times but these were brushed aside.
A coroner ruled she would most likely have survived if doctors had identified the warning signs of her rapidly deteriorating condition and transferred her to intensive care earlier.
The new constitution will also reinforce the health service's commitment to unpaid carers and will aim to reduce inequalities in access among different groups.
Louise Ansari, chief executive of Healthwatch England, said the constitution 'plays a crucial role in shaping the culture of our NHS and helping the public to know their rights'.
'Since the NHS Constitution launched, it has helped to shift the balance of power from services towards patients and their families,' she added.
'But, with only a third of people knowing their rights, there is still a long way to go.
'Given the challenges our NHS faces, a conversation to reaffirm and raise awareness of the most important rights to the public has never been more timely.'
Sir Julian Hartley, chief executive at NHS Providers, said: 'This consultation marks a once-in-a-decade opportunity to review and reset the NHS's relationship with patients.
'Trust leaders are committed to creating a responsive and effective NHS which meets the current and future health needs of all the patients and communities they serve.'