"Very little progress" has been made on the universal credit scheme despite its £700m cost to date, MPs have said.
The Public Accounts Committee said fewer than 18,000 were claiming the benefit by October 2014 - despite seven million expected claimants by 2019.
The MPs also said it was hard to judge value for money because spending had been justified on promised future benefits, not those delivered to date.
The government insisted the programme was on track and making good progress.
Labour says universal credit is "failing" and has called for an urgent review.
The benefit - which replaces six existing benefits with one single payment - began its phased roll-out earlier this month, after delays.
The aim is for it to be offered in all jobcentres in England, Scotland and Wales by 2016.
'Promise of benefits'
But the chair of the Public Accounts Committee, Labour MP Margaret Hodge, said "very little progress has been achieved on the front line".
"Fewer than 18,000 people were claiming universal credit by October 2014, out of around seven million expected in the longer term - just 0.3% of the eligible population," she said.
"We hope the [Department for Work and Pensions] expectation that this number will rise significantly by February 2016 proves to be accurate," Mrs Hodge added.
The committee has recommended that the DWP sets out what it has gained from its spending to date, saying it is difficult to judge at this point whether the project is delivering value for money.
"As the department has justified this spending on the promise of benefits in the future - such as from higher employment - rather than on the actual delivery of benefits to date, we simply cannot judge the value for money of this expenditure at this stage," Mrs Hodge said.
The report also flagged concerns over the programme's IT infrastructure. The MPs said the department's "twin track approach" of running existing IT systems alongside the development of a new digital service was "complicated and expensive" - and must not continue for longer than is required.
The committee noted the DWP "reset" the programme in 2013 to put it on a sounder footing, but said it had already fallen a further six months behind schedule for developing the digital service.
A DWP spokesman said using existing IT "ensures value for money and will save the taxpayer over £2bn".
The spokesman added: "Universal credit is on track and we are making good progress - almost 64,000 people have made a claim and this time next year universal credit will be in every jobcentre in the country.
"Latest evidence shows it's already transforming lives with universal credit claimants moving into work faster and earning more."
Labour's shadow work and pensions secretary, Rachel Reeves said the "failing" programme has been beset by "huge waste and delays".
"Labour wants universal credit to work and we'll call in the National Audit Office to do an immediate review of this failing programme to get a grip of the spiralling waste and delays," she added.
The universal credit project has been delayed a number of times since its creation and MPs and the National Audit Office have criticised the way it has been managed.