Opinions on reforming the House of Lords are becoming increasingly polarised, the lord chancellor has warned.

Lord Irvine said that MPs and peers were at risk of backing either a wholly elected second chamber or one that was entirely appointed.

Speaking on BBC Radio 4's Today programme, he argued that the issue was one of the most difficult in politics in the last 100 years.

"All bets are now off in the sense that the white paper in which the government proposed for the time being 20 per cent elected was road tested...and it didn't command acceptance.

"The real argument I think you will find, when we have our debate on the 21st and 22nd of January, is polarising around whether there should be an all-appointed or an all-elected house," he said.

The lord chancellor said that while there were critics of the government's favoured "hybrid" solution of elected and appointed peers, there was a need to "get the kind of balance that we can all agree on for today".

"I think people are now looking at the issue more fundamentally and in terms of the stability of parliament itself."

Also speaking to the Today programme, Commons leader Robin Cook said that the lord chancellor had not ruled out any one option.

"What Lord Irvine has done, and we are totally in agreement on this, is we have agreed on a strategy in which this has to be a decision for parliament. It has to be a decision on a free vote in both houses of parliament.

"There will be seven options before the Commons and Lords chosen not by the government but by the joint committee. Those do include an all-appointed or an all-elected House and there are five options in between," he said.

Cook added that he could "see a case" for a hybrid solution, but said a reformed Lords should be representative and carry the legitimacy that "usually comes from elections".

"I do not want to end up in the situation where we have been so often in the past in which there is no reform because those who want reform cannot agree on what type of reform.

"Nothing is inevitable. I myself want to see one of those options developing a commanding, convincing majority so we can get momentum into reform of the House of Lords. It may well be that that commanding majority maybe for one of the mixed options, but time will tell."

The shadow attorney general, Bill Cash, predicted that the eventual outcome would involve a largely-elected second chamber.

"I think it's a democratic principle, I think there are very distinguished members of the House of Lords at the moment who have been appointed. Some of them may well stand for election and would be elected," he said.

"I think that reality will bear down on this and I believe ultimately we will end up with a largely elected House of Lords.''