A petition calling on Asda to treat its workers with respect has now received more than 23,000 signatures.
Asda wants workers to sign the so-called 'flexible' Contract 6 - which the unions says will staff lose all their paid breaks and forced to work bank holidays – or be sacked on November 2 in the run up the Christmas.
The supermarket argues that the move will increase pay for workers.
Asda workers have been protesting outside stores up and down the country, while more than 1,000 turned out for a protest in August.
West Yorkshire Police will control traffic as a rolling road closure by deploying officers/PCSOs at junctions.
Gary Carter, GMB National Officer, said: “Asda workers know everyone is backing them– from film and TV stars to political heavyweights and the hundreds heading to Leeds to protest this week. Everyone but Asda bosses basically.
“This new contract, with the contractual changes it brings, is forcing workers to choose between looking after their disabled son, elderly mother or vulnerable partner and losing their job – it’s just not right."
An Asda spokesperson said: “The retail sector is immensely competitive and it is important that we are able to serve our customers in the best way to meet their needs.
"This contract is about increasing the take-home pay of more than 100,000 retail colleagues, through an investment of more than £80m, and ensuring that everyone doing the same job is on the same terms and conditions.
“The overwhelming majority of our colleagues from across all our stores have signed onto the new contracts and while we appreciate that some of our colleagues find the changes more unsettling, we do not want any of them to leave.
"We understand colleagues have commitments outside of work and will not be asking them to constantly move the time they work, their days or departments.”