Jeremy Corbyn has said that Britain must not be “drawn into responses that feed a cycle of violence and hate” following the terror attacks in Paris.

The Labour leader told a regional party conference in Bristol on Saturday that governments “must not keep making the same mistakes” following atrocities such as the series of attacks in the French capital that left 130 people dead.

However, Corbyn said Labour would back every necessary measure to ensure Britons were safe. “The dreadful Paris attacks make the case for a far more urgent effort to reach a negotiated settlement of the civil war in Syria and the end to the threat from Isis,” he said.

“It is the conflict in Syria and the consequences of the Iraq war which have created the conditions for Isis to thrive and spread its murderous rule,” he added. “For the past 14 years, Britain has been at the centre of a succession of disastrous wars that have brought devastation to large parts of the wider Middle East. They have increased, not diminished, the threats to our own national security in the process.”

Corbyn had been due to give his speech last weekend but cancelled it in the wake of the Paris attacks.

The Labour leader’s comments come as David Cameron seeks to build cross-party support for UK airstrikes against Islamic State in Syria. There is no schedule for a parliamentary vote on airstrikes but the prime minister could move as soon as this week.

The opposition leader is facing mounting demands to allow MPs a free vote. The shadow chancellor, John McDonnell, told LBC on Saturday that MPs should have a free vote on Syria, directly contradicting Corbyn’s stance.

Labour MP Mike Gapes said it would be “deplorable” if his party failed to back military action in Syria in the wake of the Commons vote. A string of senior figures have criticised Corbyn for insisting Labour will seek a common position – and for questioning the legality of the killing of Mohammed Emwazi, the Isis assassin known as “Jihadi John” – in a US airstrike.

Many are also angry about his continued association with Stop the War, which issued a statement in the wake of the Paris attacks suggesting the city had “reaped the whirlwind” of western interventions in the Middle East.

In an open letter to Corbyn, former shadow minister Jamie Reed urged him to act to “repair the damage inflicted to the party” in recent weeks by a series of damaging, self-inflicted stories.

Reed warned that any attempt to whip a vote on airstrikes would result in a significant number of MPs rebelling and would be a “calculated attempt to engineer a damaging and avoidable conflict” within the parliamentary Labour party.

“Matters such as this – as your own voting record shows – will always be subject to individual conscience irrespective of the party whip,” he told Corbyn.

The shadow foreign secretary, Hilary Benn, said in response to a security council vote on Friday night that saw unanimous support for countries fighting Isis that the move “must be seen as part of an overall effort to accelerate moves towards a comprehensive settlement of the conflict in Syria”.

“As we have consistently said, Labour will judge any proposal the government brings forward on British military action in Syria on the basis of what difference it would make to our objective of defeating Isil [Isis], its objectives, its legal basis and the views of other nations in the region,” he said.

“Crucially it must be part of a wider and more comprehensive strategy to end the threat they pose and achieve a negotiated solution to the Syrian civil war.”

The Liberal Democrat leader, Tim Farron, said: “The fact that Russia did not use its veto is an important first step. The UK should now use all its diplomatic skills to support the efforts being made in Vienna to assemble an anti-Isil coalition including Russia, Turkey, Iran and other key states in the region.

“At the same time, the prime minister must address the questions raised in the foreign affairs committee report when he presents to parliament the long-term strategy for any military action in Syria. That must include the planning for post-Isil Syria, which has so far been absent amid the calls for UK planes to be engaged in strikes.”