MPs are moving towards a consensus in favour of military action against Islamic State in Syria, Philip Hammond has said.

Speaking at the Conservative party conference in Manchester, the foreign secretary declared there was a growing feeling in parliament that something must be done to tackle Isis in its Syrian stronghold as well as Iraq.

“We have made a very clear commitment that before we get involved in airstrikes in Syria – other than very targeted cases where we are dealing with direct threats to the UK – yes, we would come back to parliament and get the authorisation,” he told the BBC after addressing the main hall.

“And I think there is a sense that there is a beginning of consensus now in parliament that this has to be dealt with, that we have to take the fight with Isis to Raqqa in Syria, rather than just attacking them in Iraq.”

He said he believed Russia is engaged in “classic asymmetric warfare” in Syria by using its military clout to prop up President Bashar al-Assad while saying it is attacking Isis militants.

“You have a strong propaganda message that says you’re doing one thing while in fact you are doing something completely different and when challenged you just flatly deny it,” Hammond said.

He said Britain had held discussions with Russia but kept on getting the same response - that Moscow was attacking Isis in Syria.

“You try talking to the Russians,” he said. “They just keep repeating their position - that is by the way also the Iranian position - and it is just incredible.”

He said that Britain needed “absolute clarity” that Assad would not be part of Syria’s future and rubbished proposals put forward by Russia and Iran for elections as a means to end the conflict.

His earlier comments suggest the government is feeling more confident about calling a vote in the Commons, which David Cameron will only do if he knows he can win. The prime minister would need to rely on some Labour votes, given the number of his own party who would be likely to rebel.

Although the Labour conference voted not to support strikes without UN backing, many of the party’s MPs are known to be sympathetic to the government’s aims as long as a good case is made to parliament.

The situation in Syria has been complicated by Russia’s military move into the country to aid the president, Bashar al-Assad.

While acknowledging the situation has changed, Michael Fallon, the defence secretary, confirmed the UK still wants to launch airstrikes against Isis in Syria.

He told the conference that the UK must not leave it to the US, France and Australia to defend British streets against terrorists.

He also said Britain must stand up to Russian aggression more strongly and that Russia’s president, Vladimir Putin, was changing international borders by force – something not seen since the second world war. “In the face of this aggression, we have to show that our collective resolve is stronger than ever.”

Hammond said the UK would be at the forefront of efforts to push the EU to maintain economic sanctions on Russia over its move into Ukraine.

The government’s position is that the UK is prepared to work with Russia to try to bring peace to Syria after a bloody four-year civil war. However, after the UN general assembly in New York last week, Cameron said the US and UK were miles apart from Russia and Iran, which cannot contemplate Syria not being led by Assad.

Cameron has strongly criticised Russia for propping up Assad when he has “butchered his own people”, as the prime minister said last month, and bombing rebel groups in Syria that are not part of Isis.

Hammond and Fallon used their platforms at the conference to attack the Labour leader, Jeremy Corbyn, saying his party was now a danger to UK security.

Fallon said: “How did (Labour) respond to their election defeat? By electing a leader who would weaken our national security – who would scrap Trident, leave Nato, and can’t think of circumstances in which he would use our armed forces. This is no time for Britain to retreat from the world, to let terror triumph, or to put our people in peril.”