Health minister Rosie Winterton has said that consent will remain the cornerstone of controversial organ donation legislation.

Winterton was introducing the government's Human Tissue Bill in its second reading before the Commons on Thursday.

But she resisted calls for change from doctors to make patients opt out from, rather than into, organ donation schemes.

The British Medical Association had called for a system of presumed consent to be included in the bill, but Winterton denied that this would increase the number of donors.

"There is no evidence that a policy of presumed consent increases the number of organs for transplantation," she said ahead of the debate.

"Following a comprehensive consultation process with patients and family groups, doctors and researchers, a broad consensus was achieved in favour of the measures set out in this bill.

"The concept of presumed consent therefore has no place in this bill."

The legislation was drawn up in response to the Alder Hey hospital organ retention scandal and subsequent reviews.

The tightening of the law will come alongside a fresh drive to encourage donation.

"This bill will improve public and professional confidence so that people will be more willing to ask for, and agree to valuable uses of tissue and organs like research and transplantation," Winterton said. "Donation is a gift of life and will remain so."

Shadow health secretary Andrew Lansley said Conservative MPs would be given a free vote on the bill.

"While the Conservative Party has supported the legislation, the lack of clarity in the bill that several key organisations have criticised is the result of the governments failure to conduct pre-legislative scrutiny," he said.

"The Conservative Party will not direct how colleagues vote on the issue of 'presumed consent'.

"However, I will oppose an 'opt-out' system as I believe it would be completely contrary to the general intention of the bill, which is to establish that consent is a positive step, taken with full information.

"I also believe an opt-out would, if implemented with proper safeguards, require discussion with the family and therefore will not necessarily change the fact that organ donation needs either the express wish of the donor in advance or support from their family after death."