Britain's Prime Minister Theresa May delivers a keynote speech in central London on May 21, 2019. (Photo: AFP)

British Prime Minister Theresa May said on Tuesday that the Withdrawal Agreement Bill will include a vote on whether to hold another referendum.

"I recognize the genuine and sincere strength of feeling across the House on this important issue," she said, calling it the "last chance" to get Brexit done.

She also promised measures on the temporary customs relations, environment and workers' rights to attract the support of Labor MPs.

"I knew delivering Brexit was not going to be simple or straightforward," she said, adding that delivering Brexit has proved "even harder" than she anticipated.

The Withdrawal Agreement Bill, which will implement the content of the deal with European Union, will be put to a Parliament vote in early June.