Nine out of 10 benefit claimants are not ready to deal with the government's welfare changes and are likely to lose out when it is introduced nationally in October, according to the first independent survey of recipients.

Over nine months, Citizens Advice collected data from almost 1,800 people in Birmingham, North Dorset and Wales who would have to access universal credit, a new scheme that will roll six benefits into a single payment.

The charity said its survey showed that many people would struggle to budget, did not have the right bank account or could not manage their benefits online – with the result that many could end up facing hardship and debt.

The survey results come as work and pensions secretary, Iain Duncan Smith, faces a grilling by MPs this week on universal credit's spluttering start. The charity says its findings should sound alarm bells in the government, especially as the scheme begins in October and has been dogged by rumours of IT failures.

Universal credit will require claimants to access benefits online; to pay rent themselves, rather than housing benefit going directly to landlords; and to have a bank account which can handle direct debits. Eight out of 10 people affected, says Citizens Advice, "don't have the basic information about what is about to happen".

The charity asked respondents whether they felt they would be able to cope with five possible problem areas: budgeting, monthly payments, banking, staying informed and internet access. Ninety-two per cent said they felt unprepared for the new system in at least one area.

There are concerns Two-thirds said they would need help to "get online and manage my universal credit account". Three-quarters said they could not on their own "keep track of my money on a monthly basis".

Typical is Derek Mallet, from Birmingham, currently receives employment and support allowance, due to long-term depression and more recently a heart attack. His wife is disabled and the pair's benefit income is less than £600 a month.

Mallet said he was "concerned about having to use the internet in order to set up and get benefits. I have never been on a computer." Citizens Advice said this unpreparedness was "widespread across people of all backgrounds and ages".

Gillian Guy, Citizens Advice chief executive, said: "Our report shows that an overwhelming majority of people do not feel ready to deal with universal credit. Our findings must act as a wake-up call for government.

"The results demonstrate yet again how vital it is that implementing universal credit is not left to chance. There is clearly a breakdown in the system if 90% of potential claimants are not ready to deal with this major change to their payments, and ministers must act urgently to address this problem."

She called on the government to allow claimants to request fortnightly rather than monthly benefit payments, and for recipients to ask that their rent continues to be paid directly to their landlord for the first year of the new system.

Labour said universal credit "is clearly in deep trouble". The party's work and pensions spokesman, Liam Byrne, said: "Universal credit is now in real danger of becoming universal chaos. This flagship programme is supposed to be ready in just months, but every aspect of the scheme still seems woefully under-cooked."

A Department of Work and Pensions spokesperson said the government was working with "councils, social landlords and community groups, including Citizens Advice, to offer support" to claimants.

"We have always been clear some claimants will need extra support ahead of universal credit. The four-year rollout of the new benefit will give us time to prepare people and give them the right help."