The UK’s national security council is to meet shortly to decide how many British troops to send back to Iraq to help combat the threat from Islamic State (Isis). An estimated 100 to 200 could be sent, mainly in a training role, but some would be combat troops protecting the trainers.

The council, made up of cabinet ministers and heads of intelligence and the military, will also discuss where the troops will be based. The defence secretary, Michael Fallon, said the numbers would be in the low hundreds.

A Ministry of Defence spokesman said: “No decisions on troop numbers, units or locations have yet been made”.

The Iraqi army, though trained by the US, British and other allied forces before the final US withdrawal in 2011, collapsed this year in the face of advancing Isis forces which took over much of north and central Iraq.

The British return to Iraq in a training role was announced in parliament last month but not the numbers or location.

There have been British troops in Iraq since September, based in Iraqi Kurdistan, mainly training the peshmerga militia force in the use of machine-guns. British special forces have also been in place to bolster the peshmerga, which at one point seemed vulnerable to Isis attacks.

British troops formally left Iraq in 2009 ahead of the US. The Obama administration initially hoped it could defeat Isis by air power but so far has only been able to contain it, not roll it back, which would require troops on the ground.

The US said in November it was to send 1,500 American trainers to Iraq, teaching at four centres, one in Kurdistan and three others around Baghdad. The UK could be based at one or all of them.

There are fears that providing British troops as trainers could lead to mission creep, such as sending them to accompany Iraqi forces into combat , or eventually back into combat.

Fallon told the Telegraph: “Our role now, apart from air strikes, is increasingly going to be on training. In particular it will mean dealing with car and truck bombs and roadside devices, as well as basic infantry skills.

“We have not finalised numbers yet – obviously we have got a lot of kit back from Afghanistan that we can make available – but we are talking very low hundreds.”

The UK pulled out of Afghanistan this year. The British contribution to Iraq is part of an effort by the US government to put together an international force to return to Iraq, initially at least in a training role. The German government announced on Thursday it was to send 100 soldiers to Iraqi Kurdistan.

Vernon Coaker, the opposition Labour defence spokesman, said Labour supported the assistance to the Iraqi government but he asked for clarity about the scale, scope and time-frame of the deployment.