Britain's Opposition Labour party on Friday faced a fresh crisis after one of its South Asian MPs quit her shadow Cabinet role as education minister in order to vote against a new Brexit Bill in Parliament.

Tulip Siddiq, the niece of Bangladeshi Prime Minister Sheikh Hasina, stepped away from the Labour frontbench following party leader Jeremy Corbyn's decision to impose a whip on Labour MPs to vote in favour of triggering Article 50.

"On the announcement of the three-line whip on the Article 50 vote, I feel I have no choice but to resign from my frontbench role as shadow minister for early years. I do not support the triggering of Article 50 and cannot reconcile myself to the frontbench position," the 34-year-old Member of Parliament (MP) for Hampstead and Kilburn in north-west London said in her resignation letter.

"I have always been clear I do not represent Westminster in Hampstead and Kilburn, I represent Hampstead and Kilburn in Westminster. I feel that the most effective place for me to counter Theresa May's hard Brexit is from the back benches," she writes.

Siddiq's constituency had voted in favour of remaining within the EU in the June 2016 referendum.

The European Union (Notification of Withdrawal) Bill was tabled in the House of Commons on Thursday to give British Prime Minister Theresa May the go-ahead to invoke Article 50, which will trigger the official two-year period of negotiations for Britain's exit from the EU after a June 2016 referendum in favour of Brexit.

While Corbyn wants his party to not block the bill, Siddiq has joined a number of rebel MPs who plan to defy the party line.

"In terms of the motion itself, three quarters of my constituents voted to remain and I intend to stand up for them throughout these debates. I will be looking carefully at what the government brings to Parliament, and of course any amendments that would be submitted by my colleagues in the Labour Party.

Ultimately, I will not be satisfied until there is total clarity over the measures to protect the security, residential status, and living standards of those I am so proud to represent," she said.

Corbyn, who faces a fresh internal crisis over the issue, said he understood the pressures for MPs who represent leave constituencies and those who represent remain constituencies.

"I say to everyone, unite around the important issues. I'm asking all our MPs not to block Article 50 and make sure it goes through next week," he said.

A few other Labour MPs, including senior Indian-origin MP Virendra Sharma, are also on the fence over the issue and said he is yet to decide on which way to vote next week.