Charities have spoken of their fury over changes to the welfare system which from tomorrow will force unemployed single parents with children about to start school to find a job or risk losing part or all of their benefits.

These 124,000 single parents with children aged five and six were given only eight weeks notice of the fact that they would have to move from income support to jobseeker's allowance (JSA). Previously, lone parents of older children have been given up to 12 months notice, giving them a greater chance of planning ahead and improving their skills and qualifications.

According to research to be published by the charity Gingerbread on Monday, single parents moving to JSA now also face a much harsher time finding "a family-friendly job in a hostile labour market characterised by low economic growth and high unemployment".

While the definition of their availability for work must take their childcare responsibilities into account, a lone parent could risk losing part of his or her benefits for up to three years if they are judged to be seeking work with insufficient vigour. The Department for Work and Pensions estimates that only 20% of the 124,000 are expected to find employment.

In a report called It's Off To Work We Go? Gingerbread's Philippa Newis points out that the absence of good affordable childcare, the dearth of part-time jobs and the fragile health and wellbeing of some children requiring parents to take time off work have all presented challenges to each group of single parents who have been required to find employment since the age threshold first began to be lowered in 2008. Then, single parents with children aged 12 and older had to seek employment. However, the current rate of unemployment – six people applying for each vacancy – along with insufficient help with childcare costs until the implementation of the universal credit next year and the end of financial help for some education courses for parents on income support as they prepare to move on to JSA means that the parents of these school-starters will face still further obstacles.

Level 3 is the highest vocational qualification that an individual can hold – and it significantly improves earnings mobility. Only 25% of those aged 25 to 29 who hold a level 3 qualification earn £7 an hour or less compared with 55% of those with level 1. Financial support for training is available on JSA, but a parent might have to leave a course if offered a job.

"This is a waste of public money," Newis said. "Not only in respect to loss of fees but also in light of future potential for earnings." Gingerbread has collected data from parents of children aged seven or older who have already made the transition to JSA. While many found the soon-to-be defunct lone parent advisers at Jobcentre Plus to be highly effective, other advisers "failed to grasp the added complication of trying to find a job when caring for children alone. This left [parents] feeling stigmatised and intimidated," said Newis.

A longitudinal study by Single Parent Action Network (Span) published last week, followed 50 single parents for three years and supports this view. The parents found work through friends, networks and cold calling companies but none via support from Jobcentre Plus.

A spokesperson for the DWP said: "The Work Programme is also available providing people with individualised, tailored support to find and stay in employment."

Among the recommendations that Gingerbread makes is better help to improve qualifications without losing benefits; realistic support with childcare costs; employers offering higher qualified part-time jobs and more effective advisers at Jobcentre Plus.

Fiona Weir, chief executive of Gingerbread, said: "Most single parents want to work but struggle to find family-friendly jobs that pay enough to lift their family out of poverty. Government needs to take a longer-term approach and support single parents to skill up and improve their prospects of a decent job."