The former frontbencher revealed he would go against the majority in his Rhondda constituency which backed Leave on June 23 and vote against the Brexit Bill.
The South Welsh constituency voted 5.37 per cent to leave the European Union last summer, with 46.3 per cent electing to remain.
But the Labour MP, who has represented the area since 2001, has turned his back on his own voters – essentially signing his own resignation.
Chris Bryant vowed to ignore the voices of his constituents
Speaking in Commons today, he said: "I am a democrat but I believe in the form of democracy that never silences minorities and I think the 48% in this country have a right to a voice and for that matter the 46% or the 45% or whatever the actual figure was in my constituency.
"Today I'm afraid I am voting and speaking on behalf of a minority of my constituents."
He warned the Government's Brexit plans would do "untold damage" to his constituents and make the UK "poorer" and "weaker".
But he acknowledged voting against the majority view of his constituents could cost him his job.
Theresa May's 12 point Brexit plan
Mon, January 16, 2017
It's finally here!
1 of 7
Continued cooperation with the EU to tackle terrorism and international crime.
Today I'm afraid I am voting and speaking on behalf of a minority of my constituents
Labour MP Chris Bryant
He said: "In the end there is no point in any single one of us being a member of this House if we don't have things that we believe in and that we are prepared to fight for and, if necessary, lay down our job for."
Labour former shadow transport secretary Lilian Greenwood indicated she would also vote against the Bill.
Intervening on Mr Bryant, she said: "I came into the chamber today not having finally decided which way to vote.
"Do you agree with me that if I believe the Government's plan is not in the interests of my country and my constituents then I should join you in the lobby and vote no to the Bill tonight?"
MPs have been debating the bill in Parliament for the last two days
However many used to debate in the Commons to voice their support for the brevet bill – vowing to back the opinions of their constituents regardless of their own personal opinions.
Charlie Elphicke, Tory MP for Dover, said: "I for one will be voting to respect the result.
“The leader of the Liberal Democrats seems to think this is like Hotel California – you can check out and you can never leave.
“I don't think that is the right approach to take. The SNP think you should just have multiple referendums until you get the right result.
Chris Bryant's Rhondda constituency voted to Leave the EU
"My constituents have been very clear. Number one – there must be an end to unchecked EU migration.
“Number two – no more billions for bloated Brussels bureaucrats."
He added: "It is the job of this House and the job of each and every one of its members not just to respect the result but to make it work for the British people."
The comments come after Theresa May urged Parliament to vote in support of the will of the British people in a press conference with Ireland’s Enda Kenny.
She said: “The people of the United Kingdom voted on the 23rd June last year – they voted in a referendum that was given to them by parliament by six to one.
“And the people spoke in that vote. The majority voted for us to leave the EU.
“I think it is now the job of the Government to put that into practice.
“And I hope when people come and look at the Article 50 bill they will recognise it is a simple decision – do they support the will of the British people or not.”