Labour leader Jeremy Corbyn is to impose a three-line whip on his MPs at the third reading of the 'Brexit bill' to approve triggering Article 50.
The third reading of the EU (Notification Of Withdrawal) Bill is to take place on Wednesday, and Labour MPs will be required to back the Government to start the process of leaving the European Union.
The move was agreed by the shadow cabinet, a Labour source said.
The Government's bill was voted through to the next reading last week by parliament after two days of intense debate, by a majority of 384.
But 47 Labour MPs, including Owen Smith and Heidi Alexander, went against the whip and voted 'no'.