Baroness O'Loan also claimed young healthcare professionals are leaving the UK as they cannot carry out certain tasks, arguing there is a need to "reestablish legal protection" for medical conscientious objections.
The Crossbench peer's Conscientious Objection (Medical Activities) Bill - which is being supported by the Free Conscience campaign - would apply to the withdrawal of life-sustaining treatment, human embryo research and activity linked to preparing, supporting or performing an abortion.
But her proposal split the Lords, with Labour's Baroness Young of Old Scone among those voicing their opposition and describing it as "unnecessary and potentially dangerous" given existing protections.
Lady O'Loan, moving her Bill at second reading, said: "It simply can't be consistent with conscience to say 'I cannot do this but I will you order you to do it'.
"If one delegates, supervises or supports an activity then one is not unreasonable in concluding that one shares moral responsibility for what happens.
"And there's a lot of evidence that medical professionals are suffering serious disadvantage and discrimination for their beliefs.
"A 2016 ad hoc cross-party inquiry into freedom of conscience and abortion provision specifically received many accounts by medical professionals who have experienced discrimination during their work life due to their beliefs.
"I've heard so many stories of young doctors and nurses contemplating their future, who have decided although they would dearly love to be involved in obstetrics and gynaecology, even though they're energised and feel vocationally pulled to the medicine of helping women through conception and childbirth, nevertheless they cannot do it because they could not in conscience kill an unborn child.
"That's why I've introduced this Bill.
"Its provisions seek to affirm as a matter of statute that no-one should be under any duty to participate in activities that they believe involve the taking of human life, either in the withdrawal of life-sustaining treatment or in any activity authorised by the 1967 or 1990 Acts."
Lady O'Loan said there is a "serious shortage" of healthcare professionals, adding many young doctors, midwives and others are leaving the UK for many reasons.
She said: "One of them is that those who labour at the coalface cannot engage with certain activities. We invest in their training, we need skills, it is time to accommodate them."
Lady O'Loan added her measures are not about reducing access to abortions or withdrawal of life-sustaining treatment.
Speaking against the Bill, Lady Young said she failed to recognise the NHS and healthcare system described by Lady O'Loan.
She said: "I really don't believe there are shoals of professionals in this country who feel that their rights are insufficiently represented by current law."
For Labour, shadow health spokeswoman Baroness Thornton said the current provisions to allow people to refuse certain activities on moral and religious grounds are balanced and work.
She said: "I think this private member's bill follows a trend we've seen in America with the introduction of state legislation to undermine LGBT and other equality laws with an increase of so-called conscientious objection exemptions for public employees providing public services."
Baroness Chisholm of Owlpen said the Government will "take a neutral approach" to the Bill, as it does with similar such "sensitive" matters.
The Government whip said it is the right of medical workers that they should have their personal beliefs respected, adding: "The right to object to participate in treatment is enshrined in the Abortion Act 1967 and the Human Fertilisation and Embryology Act 1990."
The Bill received a second reading and will undergo further scrutiny at a later date. But it has several parliamentary hurdles to clear, including securing time for consideration, as it bids to become law.
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