The prime minister is preparing the country for possible military action against the terror group and parliament could be recalled as early as Friday for MPs to debate and vote on UK involvement.
Sir Gerald Howarth told Premier's News Hour he wanted Britain to take action six weeks ago, but was pleased a decision would finally be made.
He said: "The strikes by the United States have been instrumental in assisting those on the ground to resist the advance of IS, which threatens to engulf the whole of that country.
"If it succeeded it would unquestionably cause massive instability in the region and affect us here at home."
David Cameron is likely to be formally asked by the Iraqi government to help with air strikes, something he says he would be unable to reject.
Speaking on American TV, he said: "This is a fight you cannot opt out of. These people want to kill us. They've got us in their sights and we have to put together this coalition to make sure that we ultimately destroy this evil organisation."
Labour leader Ed Miliband said he was "open to the possibility" of the UK joining air strikes but would not commit without seeing detailed proposals.
United States forces have recently carried out a further two air strikes on an Islamic State group area in eastern Syria.
The area was being used by militants to move equipment across the border into Iraq, the Pentagon said.
IS fighters have forced tens of thousands of Christians to flee their homes across Iraq and Syria as they try to extend their self-declared state ruled by strict Islamic law.
Sir Howarth agreed that bombing the organisation would not destroy it but said this would be a start.
"To prevent IS from making any further advances and pushing them back," he said.
He added: "No, of course bombs won't deal with the ideology.
"Ultimately, the ideology will only be dealt with when the world of Islam really takes this seriously."
More than 190 air strikes against IS in Iraq have been carried out by America since August.
So far, the UK has been supplying arms to the Kurdish Peshmerga forces fighting IS in northern Iraq and dropping aid to people in need.