The Prime Minister avoided a possible rebellion by opting for only a single-line whip, which informs MPs of the Government’s position but does not instruct them which way they should vote.
The “payroll vote” of ministers and parliamentary aides will abstain in this afternoon’s division, said Downing Street. Mr Cameron himself is not expected to take any part in the debate or division, which was triggered by an e-petition carrying more than 10,000 signatures.
It is understood that the arrangements also apply to Liberal Democrat MPs.
More than 100 MPs of all parties - including 83 Conservatives and five Liberal Democrats - have so far signed the motion, which does not represent Government policy.
Imposing a three-line whip could have set Mr Cameron on another collision course with his own MPs after last month’s bruising rebellion over an EU referendum.
However, the result of today’s vote will not be binding on the Government, so there is no question of Mr Cameron being forced to change his policy in response.