Dumped Prime Minister Tony Abbott has called for coordinated military action in Syria and Iraq to fight Islamic State.

Mr Abbott made the statements during an audience he held in Singapore, saying that Iraqi and Syrian forces needed to be backed by western troops in order to end “the caliphate” that is IS.

“This will be a long, difficult and costly engagement, quite possibly the task of decades, not years,” he said while giving the Fullerton Lecture late on Wednesday evening (AEDT).

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“The alternative is more attacks on decent people going about their daily lives.

“Islamic state or death cult as it is now increasingly called thrives on conflict … the bloodier the better and conflict will continue until it is destroyed.”

He said an ‘effective military response’ was required against Islamic State and more needed to be done than was currently occurring.

The former PM also warned the public to expect any campaign to defeat IS would be long, painful and costly.

He claimed IS was currently the biggest threat to the security and “stability” of the world.

He acknowledged previous campaigns in Libya and Iraq had been a disaster, but still said troops in Syria were needed.

The comments are the latest in a series of public statements by the conservative leader on the subject, coming only a day after a News Corp op-ed where he wrote the West’s culture was “superior to Islam”.

In that column, he called for the West not to be restricted by political correctness when holding Islam to account, and also said the faith needed to look within itself to change problems with radicalisation.

He repeated that view in Singapore saying: “It is very important that Muslims look into their hearts and ask themselves questions about their faith and resolve as powerfully and effectively as they can there has to be a spirit of live and let live.”

Mr Abbott is the most high-profile Liberal to urge for a debate on Islam and terrorism, joining cabinet minister Josh Frydenberg and other MPs who’ve made similar calls.

Another Mr Abbott ally, former defence minister Kevin Andrews, has also called for ground troops to be deployed in Syria and Iraq.

Opposition Leader Bill Shorten has told AAP it’s time for Mr Turnbull to pull Mr Abbott into line.

– with AAP