Prime Minister Sir Keir Starmer has suspended four Labour MPs over repeated breaches of party discipline.
The BBC understands Neil Duncan-Jordan, Brian Leishman, Chris Hinchliff and Rachael Maskell have had the party whip removed, meaning the MPs will sit as independents in the House of Commons.
Three other Labour MPs – Rosena Allin Khan, Bell Ribeiro-Addy and Mohammed Yasin – have been stripped of their trade envoy roles.
The party has not confirmed specifically why the four MPs have lost the party whip.
But the move comes after 47 Labour MPs rebelled against the government’s proposed cuts to welfare and forced ministers to water down their plans.
All four of the suspended MPs and the former trade envoys voted against the government’s welfare reform bill earlier this month.
The rebellion undermined Sir Keir’s authority, which was weakened after a series of policy reversals, such as restoring the winter fuel allowance to millions of pensioners.
Duncan-Jordan, Leishman and Hinchliff were all elected as Labour MPs for the first time last year.
Duncan-Jordan, the MP for Poole, organised a letter warning the government’s welfare changes were “impossible to support” without a “change of direction”.
In a statement, Duncan-Jordan said: “Since being elected I have consistently spoken up for my constituents on a range of issues, including most recently on cuts to disability benefits. I understood this could come at a cost, but I couldn’t support making disabled people poorer.
“Although I’ve been suspended from the Parliamentary Labour Party today, I’ve been part of the Labour and trade union movement for 40 years and remain as committed as ever to its values.
“To my constituents: it’s business as usual. I remain your hardworking local MP, I will continue to take up your concerns and speak up for Poole.”
Leishman, the MP for Alloa and Grangemouth, has also been an outspoken critic of the government’s shake-up of the benefits system.
He said: “I am a proud Labour member, and I remain committed to the party. I wish to remain a Labour MP and deliver the positive change many voters are craving.
“I have voted against the government on issues because I want to effectively represent and be the voice for communities across Alloa and Grangemouth. I firmly believe that it is not my duty as an MP to make people poorer, especially those that have suffered because of austerity and its dire consequences.
“It is the honour of my life to be the MP for Alloa and Grangemouth, and my priority remains representing and fighting for constituents, whether they voted for me or not.”
The BBC has asked Hinchliff for comment.
Dozens of Labour MPs expressed concerns about the government’s plans to cut disability and sickness-related benefits, in an effort to save £5bn a year by 2030.
More than 120 Labour MPs threatened to block the bill, putting the government at risk of defeat.
Ministers offered significant concessions to placate rebel Labour MPs and the diluted bill was ultimately voted through the Commons.
But dozens of Labour MPs still opposed the bill, marking a major revolt for a party that won a huge majority in last year’s general election.
Sir Keir did attempt to instil party discipline soon after the election, after suspending seven Labour MPs who voted against the government on a proposal to scrap the two-child benefit cap.
