A former Lord Chief Justice has said that “no-one has grappled with the detail” of the impact that assisted dying legislation could have on the court system.

Lord Thomas of Cwmgiedd, who held the role in England and Wales between 2013 and 2017, told BBC Radio 4’s Today programme “the process and the impact on the court system is really something about which there should be information before we decide in principle to proceed” with the plans.

MPs will vote on the proposed legislation on Friday following a debate in the House of Commons.

According to the plans laid out earlier this month, the legislation will mean that the process of assisted dying must involve two independent doctors being satisfied that the person is eligible. A person must be terminally ill and expected to die within six months.

Further to this, a High Court judge must hear from at least one of the doctors regarding the application, and can also ask questions of the person who is dying as well as anybody else they consider to be appropriate.

Lord Thomas told the BBC programme on Tuesday: “It seems to me that the one really difficult question that hasn’t been addressed in this is how is the judge to proceed, as it cannot possibly be a rubber-stamping exercise.

“There has to be a process, by which the evidence is put before the judge, and the judge will need help – will need either the official solicitor or some other body that can bring the evidence before him.”

He added: “What is not possible is to assess from the Bill the impact this has.”

The judicial process is an “integral part of the process, in working out precisely how it’s to be done”, Lord Thomas said.

“As far as I can see, no-one has grappled with the detail. And of course, as it’s an integral part of the Bill, you can’t say, ‘well, look, this is to be sorted out later’. It seems to me it needs to be grappled with now.”.

He later added: “The process and the impact on the court system is really something about which there should be information before we decide in principle to proceed.”

The vote on Friday will be a free vote allowing MPs to decide in line with their conscience, and it has meant that senior ministers have openly given a variety of opinions on the issue.

Justice Secretary Shabana Mahmood and Health Secretary Wes Streeting are among those who have criticised the plans.

Employment minister Alison McGovern told Sky News on Tuesday morning that she is still undecided about how she is going to vote on Friday.

She told the channel: “I haven’t decided how I’m going to vote. I’ve listened to my constituents who have been so kind and so generous to share with me their experiences, and I want to listen to my colleagues in the debate in full and decide how to vote.”

She added: “I think it’s so important that people are able to have a good death and that families feel that their loved one was able to die in the most peaceful way possible in accordance with their views, but I haven’t decided on this issue.”

The Cabinet is split on the issue, with more members believed to be in favour than against.

Culture Secretary Lisa Nandy, Work and Pensions Secretary Liz Kendall, Northern Ireland Secretary Hilary Benn, Transport Secretary Louise Haigh and Energy Secretary Ed Miliband have all said they will back the law.

Others, including Home Secretary Yvette Cooper, have been less explicit but indicated their support for the measures in the Bill.

Meanwhile, Ms Mahmood, Mr Streeting, Education Secretary Bridget Phillipson and Business Secretary Jonathan Reynolds have said they will reject the legislation.

Supporters of the Bill are optimistic that it has enough backing to pass the first Commons hurdle but the result will not be known until a division list is published after the vote, showing which way MPs voted.

Proponents say existing legislation fails to respect patient autonomy and discriminates financially between those who can afford to travel abroad to end their lives within the law and those who cannot.

Many of those opposed to a law change have voiced concern about the potential for coercion and mission creep, and say the legislation has been rushed.