In the Queen's Speech earlier, Boris Johnson's government committed to deliver on plans set out by his predecessor, Theresa May, who promised to make sure that restaurant waiting staff receive 100% of their tips.
It follows an outcry that some major restaurant chains - such as Giraffe and Prezzo - were keeping as much as 10% of tips paid by card.
The bill puts a legal obligation on restaurateurs to "pass on all tips, gratuities and services charges to workers without deductions".
But Unite said it has been waiting for a change to tipping laws for more than three years.
"The Tories promised to tackle the tipping abuses first with a consultation that ended in June 2016 and then with a promise of legislation over one year ago by former prime minister Theresa May," the union said.