Iain Duncan Smith has said he does not want to get bogged down in defending the "nitty gritty" details of how his new benefit system works, amid concerns the online form needed to make claims is flawed.
Universal credit, which replaces other benefits such as jobseeker's allowance, income support and other tax credits, will be introduced in four local jobcentres today in selected areas of Ashton-under-Lyne, Oldham, Warrington and Wigan.
The work and pensions secretary told BBC Radio 4's Today programme the new process of claiming benefits will be "much quicker" and "much simpler" than the current system.
"As we know over 80 per cent of all claimants on welfare are already online, we know that a huge number of them are already using computers and telephones," he said.
"The second thing is, honestly, 96 per cent of all jobs now require some kind of computer interface, so that means if you cannot go onto a computer you will only be able to apply for four per cent of the jobs in Britain. That's why we're using this process and we've been working with claimants and we'll go on working with them to get them ready to go online ."
However questioned on the specifics of the online form was overly complicated and time consuming Duncan Smith said he was "not going to end up in the nitty gritty detail".
The process of making an application for universal credit can take 45 minutes and it is not possible to save progress made, meaning if there is an error it has to be started from scratch.
But Duncan Smith insisted: "It's quicker, it's more accurate and it's easier for them [claimants] to understand."
The Public and Commercial Services (PCS) union, which represents staff in jobcentres, has said it will stage a protest at Ashton-under-Lyne.
PCS general secretary Mark Serwotka said: "If universal credit was being introduced to genuinely make life easier for people entitled to benefits it would be commendable, but the government's pernicious language exposes its real intent is to demonise and punish them.
"We have shown that ministers are prepared to mislead and misdirect to drive through their welfare cuts, so we are challenging Iain Duncan Smith and others to prove what they claim is true."