Before this year's election, Lord Carlile probably had more recent experience of dealing with the business end of government than any other Liberal Democrat in the House of Lords.

As the independent reviewer of terrorism legislation for the past nine years, Alex Carlile QC monitored the Labour government's fight against Islamic extremism at close quarters.

It has been his job to judge where the law-makers overstepped the mark and threatened the democratic values of this country. He has been highly critical of increased police "stop and search" powers. However, on "control orders" for terror suspects and pre-charge detention, he has been supportive of tough government policy, much to the consternation of some within his party and civil liberties campaigners such as Shami Chakrabarti at Liberty.

In a few weeks he steps down from the counter-terrorism post with a recognition that the relationship with the Liberal Democrats has sometimes been strained. But he is unrepentant.

"The party has been critical of my views on things like control orders and pre-charge detention as being not liberal. I reject that completely. All my views have been evidence-based. And in everything I do, my sense of justice, liberalism and proportionality leads my thinking."

Now he will have a new freedom to comment from the back benches. He intends to be as outspoken as he was as MP for Montgomeryshire from 1983 to 1997.

"When I was an MP I didn't feel many inhibitions expressing my views on any given issue," he said. "Of course, I take the Liberal Democrat whip and I believe I am as good a Lib Dem as most people. But the nature of the Lords means that the whip rests upon one's shoulders more lightly than in the Commons."

He intends to continue with his legal practice (as a leading QC he has enjoyed the patronage of some prominent clients including Paul Burrell and Mohammed al-Fayed).

As his party prepares for its annual conference, this year held in Liverpool, Lord Carlile already has some policy suggestions for the new government. Developing ideas first rehearsed in a lecture for the centre-right think tank Policy Exchange before the election, he urges the coalition to depoliticise the debate on terrorism by making secret evidence available to senior opposition figures.

This is a marked development from Tony Blair's "if you could see what I have seen" approach, to evidence acquired by the intelligence services.

Lord Carlile said: "On what should be apolitical subjects like counter-terrorism, no government gives Opposition frontbenchers the opportunity to read the evidence, such as some of the secret material relating to people subject to control orders.

"This means that when a new government appears with bland and confident statements about abolishing this and that in their manifesto, they can be brought up very short by the evidence that is put in front of them. I believe that this has happened."

In practical terms his plan would mean security vetting the Shadow Home Secretary and the Shadow Security Minister. But Lord Carlile believes this would go some way towards creating the sort of parliamentary consensus that existed towards IRA terrorism.

Lord Carlile's parents, Jewish refugees from Poland, both converted to Christianity and the peer describes himself as a "pragmatic utilitarian". But he is proud of his "100 per cent Jewish ancestry" and is a strong supporter of Israel.

He understands concern within the Jewish community about the commitment of the coalition to Israel and, in particular, his own party's stance.

"Nobody expressed their support for Israel and of the Jewish people more strongly than Gordon Brown," he said. "I don't think there will be another Prime Minister in the foreseeable future who will express their support for Israel in quite such an unequivocal way."

He noted: "There is no political party in this country which will say that everything the state of Israel is doing is right and everything the Palestinians are doing is wrong. And indeed only an idiot, frankly, would say that."

He feels that on civil liberties Israel has been "demonstrably and inexcusably wrong", but also acknowledges that human rights organisations have reported serious abuses carried out by Hamas in Gaza.

On one issue he is categorically critical of the successive British governments and the international community: the funding of extremism through "charitable" front organisations.

"I believe that there is evidence of charitable funding collected in this country being channelled through to Hamas and possibly to other Islamist extremist organisations. I believe that the British and international authorities have done nothing like enough."

The Lib Dem peer reserved his fiercest criticism for his controversial colleague Baroness Tonge, who called for an investigation into claims that the IDF was harvesting body parts while helping with the aid operation in Haiti earlier this year.

"I thought the comments were completely outrageous, inexcusable and incomprehensible coming from a person with such a strong political record," he said. He made personal representations to Nick Clegg and Lord McNally, the Lib Dem leader in the Lords, but felt the party was "slow to take the appropriate sanctions" in removing Lady Tonge as a frontbench spokesperson. "If a person makes comments of that kind, however strongly felt, it makes them an ill fit in a party that has the word 'Liberal' in its title and means it."

Lord Carlile believes Baroness Tonge's comments did the party serious electoral damage and helped lose the two north London seats of Hampstead and Kilburn and Islington South and Finsbury to Labour. "My belief is that remarks taken as antisemitic had a significant effect on the results in those two very marginal north London seats," he said.

As for the future, Lord Carlile recognises his party has much to do to win back the trust of the Jewish community. He identified a new confidence among younger Jews and their families.

"You will find many highly educated, influential Jewish families coming together on Friday nights and making renewed contact with their religious traditions, albeit in a very modernistic kind of way… Those very Jews are natural part of any Liberal Party's support base."

With his experience of counter-terrorism and nuanced approach to foreign affairs, he would surely be an asset to any government. Would he accept a ministerial post?

He replied: "I have absolutely no plans other than to enjoy the relative independence of the back benches in the Lords and to get on with those parts of the legal practice that I enjoy."

David Cameron and Nick Clegg take note: that was not a "no".