Bosses 'have a duty of care to all staff, no matter what type of contract'
Employers are being urged to improve the way they treat agency staff or those on zero hour contracts after a study found many only give 48 hours notice of shifts.
Citizens Advice said its research found a minority of firms have practices which make it "challenging" for many on variable hour contracts to manage their work-life balance.
Employers are not letting staff specify when they can work but do not allow them to turn down shifts, leaving people in the dark about how much they will be paid from one month to the next, said the charity.
Its survey of 1,100 managers in England and Wales found one in five said staff were not able to turn down a shift, a similar number did not allow employees to specify times or days when they were unavailable, while 7% gave less than 48 hours notice of their shifts.
One man turned to Citizens Advice for help as he was on a zero hours contract, working anything from 20 to 70 hours a week, and rarely turned down shifts because of the threat of not being offered any more hours.
He said: "Thankfully I always have enough to cover my rent, but it's hard as I don't ever know how much money I will earn, which makes it hard to plan ahead for things."
Gillian Guy, chief executive of Citizens Advice, said: "The world of work has changed dramatically in recent years but employment practices have not kept pace.
"While flexible hours work well for some people, many find that the unpredictability and short notice of shifts makes managing life around their job a huge challenge.
"Childcare and study are just two examples of plans where you need more than 48 hours to arrange, but for some people turning down work is simply not an option.
"The Government is already taking welcome action to tackle some of the root causes of insecurity in the labour market, such as through its review of modern employment, investigation into the rights and treatment of non-permanent staff and increased investment in minimum wage enforcement.
"But government intervention alone cannot solve insecurity in the labour market. Employers also have a key role to play.
"Bosses have a duty of care to all of their staff, no matter what type of contract they're on.
"Steps such as better management of flexible workers and transparency around workforce make-up could transform the labour market and deliver real improvements to the ever growing ranks of flexible workers."