Conservative MP Chloe Smith says she is "prepared to back UK action, with all of its risks", in order to protect civilians.

She adds her "heart and head" say the UK should take action against IS.

Just tuned into the Syria air strikes debate? We've compiled some of the key contributions here.

There's more footage on the 'key video' tab above.

Labour defence spokesman Lord Touhig says today's debate in the Lords shows that "this House adds value to our parliamentary system". However, he adds, it is right that the Commons takes the decision on air strikes.

He says he has concerns, including about "post-conflict management." If there are insufficient ground forces "then anarchy, terror and much more will follow", he claims.

The former Labour minister calls for a diplomatic and humanitarian effort but tells peers that "the destruction of this most evil of terror groups must be our main focus".

Labour's Toby Perkins says he "envies" people who are certain of the right course of action to take.

He says that "as an internationalist" he finds it very hard to turn his back on a United Nations resolution, but he has not heard an answer to the "central issue" of ground forces.

Labour's Rachael Maskell says "it is clear that this strategy is weak" and the motion is wrong. She says she will be voting against air strikes.

Conservative Mary Robinson says: "Daesh poses a direct threat to the UK."

She says that when the UN calls on states to "take all necessary measures", the UK has a "responsibility to answer that call" and she will be voting with the government.

House of Lords
Parliament

Liberal Democrat foreign affairs spokesman Lord Wallace of Saltaire says that people are sceptical of the case for another UK military campaign in the Middle East. People need to be persuaded that the government will work for reconciliation in Syria and "between Saudi Arabia and Iran", he argues.

Lord Wallace says the government has "engaged" with the Lib Dems on the party's "conditions" for action, while the recent UN resolution "addresses the legality".

He adds that "bombing alone is not enough" and must be accompanied by diplomatic and humanitarian efforts.

Labour's Sir Keir Starmer, the former director of public prosecutions, says that air strikes would be lawful but he is not convinced by the case for war.

He says he is "not against air strikes" in principle but they will not be effective without ground forces, and that the idea of 70,000 opposition ground troops suggested by the prime minister is "unrealistic".

House of Lords
Parliament

Another former UK ambassador to Syria, crossbench peer Lord Wright of Richmond, says the UK is already providing intelligence support to international forces opposing the Islamic State group. "Should we not leave it at that?" he asks.

He argues that, "however much it sticks in our throat", the UK should accept that the only forces fighting Islamic State effectively are President Assad's "Russian allies".

He also has some words for politicians who have been calling for IS to be referred to as "Daesh".

Labour's Stephen Doughty says he will be voting in favour of air strikes tonight. 

He says "we have a clear UN resolution", as well as "a call from our allies." He adds that there is a "direct threat" to UK citizens from IS.

Conservative MP Bernard Jenkin says it is wrong to think the West has caused this problem, adding: "If we just disengage, they're not going to leave us alone."

He tells MPs: "Paris was an act of war."

Laura Kuenssberg
BBC political editor

On days like today, we want Parliament - the institution, the people who serve in it - to impress. What can be more serious than going to war?

Today, however, Parliament did not rise to the occasion. It stumbled. In this particular drama, the question of whether to go to war (and putting our armed forces in harm's way) seemed to dwarf the players asking it.

The prime minister - the man who created this great occasion - was not at his best. The same was true of the Labour leader. Yes, he stuck to his long-held principles but they weren't presented coherently.

Happily, the eloquence missing from the front bencheswasdisplayed on the backbenches. 

But where - presuming David Cameron triumphs tonight - will today leave us? 

For all his shortcomings, Mr Cameron has demonstrated his understanding of the art of the possible: it would appear he has made his move at the right time.

And if he wins, victory will embolden him. He must know, however, that while getting into a conflict is one thing, getting out is another.  A clean exit from action in Syria is a long way off.

For Jeremy Corbyn - undoubtedly in step with many of his party members - today has once again underlined how trust between him and his members of Parliament is weakening.

Yes, the key players have failed to shine in the limelight today but we should be under no illusion: the political canvas has changed.

House of Lords
Parliament

Crossbench peer Lord Green of Deddington, a former UK former ambassador in Syria, says he is "no defender" of the Assad regime but is concerned about the consequences of its overthrow.

"These are revenge societies and what you would see is revenge on a terrible scale," he claims.

SNP MP Philippa Whitford says "the chance of chaos is high" and she does not believe "air strikes will work" in Syria.

She asks what the ground forces in Syria will become if the UK supports them.

Recounting the atrocities committed by IS, Labour's Ruth Smeeth says: "I cannot look myself in the mirror every day if we are allowing this organisation to thrive."

She says the UK "must not fall into the mindset of isolationism", adding: "We will all enter the division lobbies tonight with a heavy heart."

She says that she will be voting in favour of air strikes.

House of Lords
Parliament

Liberal Democrat peer Lord Oates condemns so-called Islamic State but calls for a political settlement.

He says the UK would be joining the Syrian conflict as "protagonists" who, as a result of a policy of opposition to President Assad, would be committed to "regime change".

If the Assad regime falls, he asks, "what will prevent the Syrian Arab army turning its fire on the moderate forces, with Russian backing?"