Labour leadership candidate Rebecca Long-Bailey has promised to give employees the right not to be contacted outside of working hours.
The shadow business secretary says the move will help end “24/7 work culture”.
Her campaign team have revealed few details about how the policy would be implemented.
It could be along the lines of France’s “right to disconnect”, which obliges companies with more than 50 workers to define employees’ rights to ignore their phones.
Ms Long-Bailey told BBC Breakfast: “Aspirational socialism is about us all rising together, and that means coming together to collectively solve issues that are damaging our mental health and stopping us getting quality time with our families or in our communities.
“We can all do better with aspirational socialism, through pushing for an end to the 24/7 work culture, and with trade unions empowered to negotiate this, we can work hard, be paid for the work we do and keep that precious time with our friends and family, uninterrupted by emails or demands.”
Ms Long-Bailey, MP for Salford and Eccles, is one of four candidates to succeed Jeremy Corbyn as Labour leader.
They have all made it through to the final ballot of party members after winning sufficient levels of support from constituency parties and Labour affiliates – apart from Ms Thornberry.
She is battling to win the requisite support ahead of the 14 February deadline.
A winner in the contest will be announced in early April.