The Prime Minister has called members for a special meeting on 24 September – one week before the Birmingham conference.
Tories are promised that a discussion about immigration is high on the agenda, according to The Times.
It comes when Theresa May clings to power amid allegations that Brexit rebels are planning to expel the leader in a party coup if she refuses to change her Checkers plans.
On Wednesday, MEPs attended a meeting of the European Research Group to "openly discuss" how to "throw" Ms. May.
But Brexiteer and ERG chairman Jacob Rees-Mogg denied that there was a threat to Mrs May's premeditation.
Up to 50 MPs threaten a vote of no confidence, according to parliamentarians.
If 48 letters were submitted to the Committee of 1922, a vote of no confidence would be activated.
Despite the increasing pressure, Theresa May has yet to propose a post-Brexit plan for immigration.
But the prime minster remains united with Sajid Javid for a global migration scheme.
This could mean that when Britain leaves the EU, the preferential treatment for EU citizens is likely to end and that they may be subject to non-EU citizen restrictions, including visa applications.
Caps may also be placed on the number of skilled and unskilled workers entering the UK from the EU.
But Whitehall sources predict a tense confrontation with migration as a result of concerns about colleagues' global plan, including chancellor Philip Hammond and business secretary Greg Clark.
But Brexiteers are likely to welcome tougher rules on migrant workers from the EU and will reject all plans that provide freedom of movement.
Net migration dropped for the first time in three tears below 250,000 earlier this year, but it remains above the promised 100,000 target that was first set by David Cameron's Tories in 2010.
Ms. May has previously hinted that she will fight against the level of immigration below 100,000 in 2022 – the end of the next five-year parliament despite pressure from her own cabinet to destroy the controversial goal.