The bill is due to be debated in the Assembly on Tuesday.
Sinn Féin are to bring forward a proposal to delay passing legislation that would see the region's welfare system overhauled in line with changes in the rest of the UK.
Key reform features include a universal credit to cover a range of benefits, housing benefit reforms and a personal independence payment reassessed every three years to replace Disability Living Allowance.
Speaking to UTV at the Tory Party conference in Birmingham, Mr Cameron said that delaying the proposals would have negative consequences for Northern Ireland.
People in Northern Ireland go to work, work hard, pay their taxes, and those taxes have been, where we came to power, supporting people living in London claiming housing benefits on homes that cost them £40-£60,000 a year.
He added: "Now how do people in Northern Ireland feel about that?
"Second point, equally important, there are people who suffer from generational unemployment," he continued.
"The work programme and welfare reform says to those people we will pay work providers serious amounts of money to help us get out of worklessness, out of poverty, and into sustainable work, so for those reasons welfare reform is good for Northern Ireland."
Sinn Féin MLA Alex Maskey says the Welfare Bill targets the most vulnerable and disadvantaged in society.
He said the measures being brought in by the Tory government are a direct consequence of the Assembly not having the "necessary fiscal powers".
Mr Maskey said: "We will press for fundamental changes to this Bill to ensure the maximum protections for those on benefits and in low-paid employment."
The impact of Sinn Fein's intervention will depend on support from other parties.
The DUP claims that if welfare reform changes are not implemented in the region in the next two years the Stormont executive will face a bill of over £200m.
On Monday Health Minister Edwin Poots warned that to not go ahead with the reform, which is being heralded as the biggest welfare shake-up in more than six decades, would mean millions lost from his department and ultimately would cost lives.
If we don't proceed with welfare reform and stay with parity, we will actually have longer waiting lists for hip operations. We will have longer waiting lists for people requiring heart surgery. We will have people dying as a consequence of that.
"Were we to do something completely daft and cost this Assembly in Northern Ireland £220m, that would probably cost us in this department around £100m," he told the assembly.
Speaking at the Tory Party conference in Birmingham, Chancellor George Osborne announced a further £10bn worth of UK-wide welfare cuts on Monday.
He said that the rich would be targeted to reduce the deficit through the "ruthless pursuit of tax evasion".
But he added: "It is wrong that it's possible for someone to be better off on benefits than they would be in work."
Among those likely to lose out from the welfare cuts are under-25s, who look set to be stripped of housing benefit and unemployed parents, who may face reductions in the amounts of support they get for additional children.
Deputy Prime Minister Nick Clegg signalled that Tories will face resistance from Liberal Democrats within Government to the welfare cuts.
Meanwhile, Mr Cameron told UTV Northern Ireland has made a good case for corporation tax and that the Government has "good faith" in devolving powers to Northern Ireland.
He said: "There are difficult issues in devolving corporation tax to one part of the UK but I think Northern Ireland has a particularly strong case because of the land border with the Republic which has that low rate of corporation tax that's why we're in these discussions, why we're going through the details, and we're looking very carefully at how to make that work."