Assisted dying could remain unavailable in England and Wales for four years if MPs vote for it to be legalised.

A proposed change to the assisted dying bill would delay the deadline for when it must be fully implemented from two years to four.

But it could come into force earlier and a spokesperson for Kim Leadbeater, the Labour MP behind the bill, described the four year time limit as “a backstop”.

The spokesperson argued changes to the bill – including new panels to oversee applications – will “inevitably take longer to implement”.

If approved, the bill, which is currently being considered by MPs, would allow terminally ill adults expected to die within six months to seek help to end their own life.

Opponents warn that people could be put under pressure to end their lives. They want improvements to palliative care instead.

But supporters argues the law needs changing because some people have horrible deaths, however good their end-of-life or palliative care is.

MPs are debating the amendment in a committee scrutinising the proposed law line-by-line.

The committee is hoping to finish going through the bill on Tuesday evening.

A spokesman for Leadbeater said: “Kim has always been clear that it’s more important to get the assisted dying legislation right than to do it quickly.

“The bill now contains even stronger safeguards than when it was first tabled, with a new judge-led Voluntary Assisted Dying Commission and multi-disciplinary panels to examine every application. These will inevitably take longer to implement.

“But the four year limit is not a target, it’s a backstop. Kim hopes and believes the service can be delivered more quickly if it becomes law later this year.”

MPs voted in support of a proposal to legalise assisted dying in England and Wales, in November 2024.

The historic vote saw 330 MPs support the assisted dying bill, and 275 reject it.

MPs were given a free vote on the issue, which meant they could make their own decision rather than follow party instructions. The government is impartial on the issue.

Months of detailed scrutiny and further votes in Parliament are required before the bill could become law.

Changes have already been made by the committee of MPs examining the bill.

For example, under the original proposals, a High Court judge would have to approve each request to end a life.

But Leadbetter suggested a three-person panel comprising a senior legal figure, a psychiatrist and a social worker should oversee applications instead.

The MPs reviewing the bill have agreed to adopt this approach.

At present, laws throughout the UK prevent people from asking for medical help to die.

However, proposed laws to give terminally ill adults the right to choose to end their life have been agreed in the Isle of Man, which is part of the British Isles.

While it remains illegal in most countries, more than 300 million people now live in countries which have legalised assisted dying.

Canada, Australia, New Zealand, Spain and Austria have all introduced assisted dying laws since 2015.