Having to pay upfront monthly childcare costs of hundreds of pounds while dealing with slow and unfathomable universal credit bureaucracy is preventing single parents from returning to work, MPs have heard.

Giving evidence to the Commons work and pensions committee on Wednesday, a group of mothers said accessing childcare support through the new benefits system – a key part of government plans to encourage parents to return to work – was stressful, complex and unwieldy.

Although 85% of childcare costs are reimbursed under universal credit, low-income parents face upfront monthly fees to childcare providers – as much as £1,500 in some parts of the UK – meaning many can’t afford to move back into work.

The difficulty of finding upfront fees was compounded by administrative delays that meant parents could wait up to two months for the money to be repaid, putting them into debt or forcing them to turn to grandparents for help, the committee heard.

Vikki Waterman, 34, who has two children aged two and four, said she would need to pay upfront childcare costs of £1,300 to be able to return to work. “I do not want to sit at home. We want to be able to go out to work and provide for our families but at the minute it is like there is a roadblock everywhere we turn.”

Although the government offers loans to help parents pay upfront childcare costs, the committee heard this service was not always advertised by staff, who often seemed unaware of how to help claimants navigate the process.

Thuto Mali, a north London mother of a two-year-old, said she had been forced to turn down a job paying £32,000. She had calculated that moving off benefits would have left her with just £2 a day to live on as she would no longer qualify for childcare costing £1,500 a month, or rent support.

“Unfortunately I was not able to take the job as work didn’t pay,” she told MPs. “Under universal credit, for me to be working simply doesn’t work … It’s not that I don’t want to work, it is just that work doesn’t pay.”

Gaynor Rowles, a self-employed hairdresser with three children aged under nine, said being on universal credit over two years had been difficult and stressful and had left her reliant on loans and gifts from her parents to make ends meet.

Claiming back childcare costs was a clumsy and slow process, MPs heard. Parents often had to take childcare receipts to the jobcentre in person, or send them by post as the universal credit system did not allow them to be scanned and emailed.

The single parent charity Gingerbread told MPs that childcare costs should be paid directly to the care provider by the jobcentre, reducing the burden on parents. Director of policy, Dalia Ben-Galim, said universal credit childcare issues meant many parents saw going into work as a risk.

A government spokesperson said: “We are doing more than ever before to support parents with the cost of childcare and by 2019-20 we will be spending around a record £6bn on childcare support.

“Under universal credit, working parents can claim back up to 85% of eligible childcare costs, compared to 70% of costs covered under the previous legacy system. This is the highest level of support ever. And if someone has accepted an offer of paid work, they are eligible to be paid these costs for the month prior to starting work.”

Universal credit rolls together six so-called “legacy” benefits into one monthly payment. The aim was to simplify the benefits system and improve incentives for claimants to move into work, or work more hours.