Employees will have the legal right from Saturday to request flexible working from their first day in a new job.
Previously, it applied only when someone had worked for their employer for 26 weeks or more.
Peter Cheese, the chief executive of the Chartered Institute of Personnel and Development (CIPD), said the new right could benefit millions of workers.
He added: “Flexibility around time, scheduling and place of work can be transformative in opening up opportunities for people to get into and stay in work, especially those who have health conditions, caring responsibilities, or other life choices they want to make.
“With an ageing population, and rising levels of economically inactive people due to ill health, flexible working is more important than ever, and has been shown to support better wellbeing, making it good for individuals as well as organisations.
“The pandemic accelerated the understanding of flexible working, and the demand for it, and many organisations have responded positively by introducing more flexible working policies.”
The conciliation service Acas published a new statutory code of practice on requests for flexible working alongside guidance.
The Acas chief executive, Susan Clews, said: “There has been a global shift to flexible working following the pandemic, which has allowed more people to better balance their working lives, and employers have also benefited from being an attractive place to work.
“Our new code aims to foster flexible working further and covers the new law changes. It sets out good practice on flexible working requests and will help employers and employees avoid any pitfalls.
“There are many types of flexible working such as part-time working, flexitime, job sharing, staggered hours, hybrid and home working.
“The starting position for businesses should be to consider what may be possible.”
A study of 4,000 workers by campaign group Timewise found that half would consider asking for a flexible pattern of work using the day-one right to request in a new job.
The Timewise chief executive, Claire Campbell, said: “The new legislation will help job hunters feel entitled to ask about flexible working options and requests could start coming thick and fast.
“Flexible working and diversity and inclusion are interwoven, and businesses that make the most of the opportunity could really open some doors to new and exciting talent.”
Research by campaign group Pregnant Then Screwed found that mothers were twice as likely as fathers to ask for flexible working after parental leave.
Joeli Brearley, the chief executive of the group, said: “Mothers are more likely to shoulder the lion’s share of the unpaid labour required to care for children and manage a household. As a result, they are more likely to need flexible working. Just three in 10 job adverts offer flexibility, limiting the progression opportunities and earning potential of mothers.
“Then we wonder why the gender pay gap widens when couples have children and continues to widen further over the subsequent decades.”
