Nick Clegg and Chris Huhne have been answering questions put to them via the BBC news website.
Click on the video on the right hand side to watch Chris Huhne answering your questions.
Nick Clegg agreed to answer your questions by e-mail. Below are the questions put to him and his replies.
Q: Do you think we can rely on border control to control immigration?
Chris Peacock, Notts, United Kingdom
A: Liberal Democrats were the first to advocate a unified border force - a policy that's now been adopted by the Conservatives and, in diluted form, by the government. We need to make sure we know who's coming in and going out of our country if we are to have the managed immigration system we all want to see: so we need to reintroduce exit checks as quickly as possible. There's currently no way to know if someone who's come here on a visa has left the country or not!
But border control is not enough. To manage immigration, we need a system that works - so the immigration service should be put at arms length from the government so political considerations don't interfere with day to day management. Asylum should be run by a wholly separate agency, as is done in Canada, where only 1% of decisions are overturned, unlike in Britain where the whole system has been in meltdown many times.
And to cut illegal immigration we need to focus the efforts of immigration enforcement officers on tackling people-trafficking, criminal gangs, and illegal working. That's why I've advocated a limited regularisation programme for people who have been here clandestinely for a decade, have no criminal record, speak or will learn English, and just want to work and pay taxes. Instead of spending £11,000 deporting these "soft targets" we should be focusing on the gangs and traffickers that bring people here. The alternative is - as Labour and Conservatives propose - to ignore the up to 600,000 people here illegally, and effectively condone a massive illegal industry
Q: Do you support the establishment of an English Parliament, or at least sessions of the English Parliament to sit at Westminster without MPs from the other British nations. If not - please explain what you mean by federalism.
Doug , Edinburgh
A: There is a real anomaly in the way Scottish MPs vote on English matters - but it is only one of countless anomalies in our electoral system, and they all need to be addressed together as part of a new constitutional settlement. Focusing on the West Lothian issue alone just plays into the hands of people who want to break up the United Kingdom.
The real English Question is in a sense the same as the Scottish Question or the Welsh Question - it's about breaking down an overbearing, over-controlling central state and returning power to local communities and to individuals. I don't think that English people primarily see this as a question of exact symmetry - the question is one of democratic control. The answer isn't to try and divide MPs into sheep and goats and risk creating problems whereby one party is in government, but doesn't have a majority for English affairs.
We need to move beyond this sterile debate and look to devolve power within England, and continue the push for a whole new constitutional settlement. Remember - every decision not taken in Whitehall is a decision where the West Lothian Question doesn't apply.
Q: What would be your immediate foreign policy reform area if elected as a leader of the Lib Dems?
Bekele Woyecha, Swansea, United Kingdom
A: I would reverse the decision to allow parts of the US Son of Star Wars missile system to be sited on UK soil. Britain has been signed up to this unilateral US programme without any meaningful debate or scrutiny in parliament.
Ballistic Missile Defence is having a profoundly destabilising impact on international relations and arms control, and risks creating a 21st-century "arms race". Russia is about to pull out of the landmark Conventional Forces in Europe Treaty and has resumed a programme of long-range patrols by Russian bombers.
America is, of course, a vital ally of Britain, but it was a serious mistake to sign up to Missile Defence so unquestioningly. Britain is not the 51st state. We must act in our own national interests, not just accede to the demands of the Pentagon.
Q: I would like to know which party would the Lib Dems support in case of a hung parliament, with the Lib Dems in the position of king makers?
Rishi Gosain, Sale, United Kingdom
I will not limit our party's ambition by talking endlessly of coalition deals, as if we are somehow campaigning to come third.
That isn't good enough for me, and it isn't good enough for Britain. We must campaign to make Britain a more liberal place, by reaching out to new
voters, winning people over to our cause, and winning more votes and seats than ever before.
I will never define our party by cosying up to other parties, or carrying on endlessly about the terms and conditions of hypothetical coalition deals. We are an independent party, not an annex of the Labour or Conservative parties. My aim is to break apart forever the stifling two-party system, not prop it up.
Q: As the Tories have moved to the left and Labour to the right what theoretical point in space do the Lib Dems occupy?
A: I'm a Liberal. I will never use the language of our opponents - the language of left and right - to define where we stand. The old stale debate between left and right is over: people no longer believe there are only two answers to every question, only two ideas it's worth having. As Britain faces the challenges of our future - globalisation, social immobility, climate change, fear and insecurity - it's liberal ideas, not the old politics of left and right, that offers the answers.
Q: What is your position on extending the use of nuclear power?
A: I will always look at the evidence on nuclear power, but at the moment it is absolutely clear to me that on grounds of cost and on waste disposal, there is no case at all for a new generation of nuclear power stations.
Nuclear is not, let's remember, carbon neutral. If you look at the life-cycle carbon footprint of nuclear and take into account processes of extraction, construction, maintenance and transport that is very clear. Nuclear power has already left behind huge amounts of radioactive waste, some of which will remain for thousands of years. No long-term, safe and viable storage solution for this waste has been found. New nuclear would only exacerbate this problem and leave a more sizeable toxic legacy for generations to come.
And nuclear is hopelessly uneconomic. A new generation of nuclear would cost at least £17bn that would swallow up much of the funding available for the research and development of a mixed basket of renewable energy sources, which would be disastrous.
Q: Most Lib Dems disagreed with the war in Iraq. If you were Prime Minister, would you pull the troops out now (as many people want) or would you stay the course to make sure that we clean up the mess we created?
Ian G-B, London, United Kingdom
It is time to get our troops out, as quickly as is safely possible. But that's because they are now doing more harm than good. We cannot walk away from our moral obligation in Iraq - walk away from the mess we have created. But we cannot wash our hands of the greatest foreign policy mistake of our age.
So we must do everything we can to promote peace in Iraq. I would start by pushing for a UN-led regional contact group to involve all local powers. We need also to accept that we may need to make significant financial support in years to come in the shape of funds for refugees, allowing refugees to Britain, supporting NGOs and other non-military assistance. Pulling troops out is necessary - but it should not be a considered the end of our obligations to Iraq.
Q: Do you think that the shameful way that Charles Kennedy was got rid of and replaced with Menzies Campbell, who many saw as being a spent force anyway, has in any way damaged the Party?
Chris Dare, Turner's Hill, UK
A: There is no disguising the fact that it has been a difficult time for the party over the last few years. I've made it clear throughout my campaign that it is time to draw a line under that period, and use this opportunity to talk - plainly and directly - to the British people. We need to become a positive, outward looking party again.