Iain Duncan Smith has said the Government's controversial benefits crackdown will teach parents that "children cost money" and put pressure on them not to have a third child.
The Work and Pensions Secretary has also warned voters will kick the Tories out of power at the next election if they become obsessed with who is its next leader against a party conference "beauty parade" between George Osborne, Theresa May and Boris Johnson.
Mr Duncan Smith's comments on slashing tax credits, top-up payments given to low-paid working families, comes a day after Health Secretary Jeremy Hunt said the reform would help encourage a Chinese work ethic among Brits. David Cameron later said he was mis-quoted.
In his conference speech, the former Tory leader outlined how his reforms were about "ending poverty, not entrenching it", and being fair to the "vast bulk of taxpayers who pay for other people’s welfare while taking responsibility for themselves".
He added: "That’s what the limit on Child Tax Credit for more than two children is about – bringing home to parents the reality that children cost money and if you have more kids you have to make the choices others make and not assume taxpayers money lets you avoid the consequences of such choices."
During a fringe event later at the Manchester conference, Mr Duncan Smith suggested the party looks "venal" if colleagues now pitch to take over from David Cameron when he stands down in 2020.
He told the Centre for Social Justice event: "The Prime Minister has said he will serve a full term. I hope this will be the last conference - I am sure it won't be - when we have a running beauty parade.
"I would certainly say to them 'honestly you have to get it under control'. My suggestion is that there is plenty of time for all that.
"If the public sees that we are so venal that we assume that we have a right to be in power in five years time they will do their level best to kick us out."
WATCH: Iain Duncan Smith tells Theresa & Boris to shut up & get on with the job (I paraphrase). Full clip here: http://t.co/5iffSCPlfb— Chris Ship (@chrisshipitv) October 6, 2015
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