He was warned by grandee Lord Kinnock to be “choosy” about who he lets in after posing alongside the defecting MP, who controversially defended her sex offender husband.
Former Conservative colleagues of Elphicke — whose Dover constituency is at the heart of the migrants crisis — were also in disbelief last night that she had jumped ship just weeks after she condemned Labour for having an open borders policy.
A beaming Sir Keir was yesterday pictured with his new recruit in his office alongside the Union Jack.
But the shock transfer was met with a wave of hostility from both sides of the political divide, with Sir Keir accused of scrapping his principles.
Lord Kinnock, Labour leader from 1983 to 1992, warned: “We have got to be choosy to a degree about who we allow to join our party because it’s a very broad church but churches have walls and there are limits.”
Senior Westminster-based GMB trade union boss Jenny Symmons said: “Labour has welcomed her in . . . without seemingly having standards you have to meet.”
She has written to the chief whip demanding a meeting about vetting wannabe MPs.
It comes after Elphicke defended husband Charlie, her predecessor as MP for Dover, until he was convicted of three charges of sexual assault against two women.
She was one of five senior Tory MPs who improperly attempted to influence the trial judge. She revealed that their 25-year marriage was over after he was convicted and jailed in 2020.
One furious Labour MP said last night: “It’s absolutely bonkers. Has anyone done any due diligence on her? This leaves a very sour taste in the mouth.
“It reveals the leadership are happy to trade the principles they do have for a short-term hit.”
Another said her move had gone down like a “cup of cold sick”.
Elphicke, who took over her husband’s Dover seat, has also repeatedly attacked Labour on migrants. She said the Government’s plan to stop the boats was “vital” while Labour’s attempts to undermine it are “dangerous”.
The Conservatives yesterday posted an article written by her, headlined: “Don’t trust Labour on immigration”.
The party said: “Even Labour MPs know you can’t trust Labour to stop the boats.”
Tory MPs did not look gutted, they just shook their heads in disappointment…
By JACK ELSOM, Chief Political Correspondent
IT couldn’t be her – could it?
That was the collective reaction when a woman looking suspiciously like the Tory MP Natalie Elphicke was spotted sat behind Sir Keir Starmer on the Labour side of the House of Commons chamber.
The time was just before noon and Rishi Sunak was moments away from his weekly bout with his Opposition rival.
Following a bruising set of local elections, the PM was keen to get back on the front foot by rallying his Tory troops.
But it soon became clear that he had walked into an ambush.
It WAS Natalie Elphicke, Labour spinners confirmed as political journalists hurried to break the news.
A statement from their new recruit blasting her old party was promptly released to cause maximum damage.
But for all the brief excitement, it proved a bit of a damp squib.
Far from detonating a political bomb under PMQs, it was barely referenced beside a quick gloat from Starmer at the top.
Tory MPs did not look gutted – they just shook their heads in disappointment.
In fact her defection only served to stir the Conservative benches into full voice cheering their leader.
Especially when within moments of her crossing the floor, Elphicke’s past disparaging comments about Labour emerged.
A neat coup for Starmer, but not a body blow by any means.
Elphicke also branded her new boss “Sir Softie” before a crunch immigration vote last year.
Tory MP Dame Andrea Jenkyns slammed the decision to defect, saying: “You were a centre-right Conservative, Labour want to give asylum to 50,000-plus people.
“I thought you had more conviction than to join the lefty Labour lot you despised so much!’’
Northern Ireland minister Steve Baker said he has been “searching in vain for a Conservative MP who thinks themself to the right of Natalie Elphicke”.
She also caused controversy for taking aim at anti-poverty campaigner and England footballer Marcus Rashford after he missed a penalty in the Euro 2020 final.
She said: “Would it be ungenerous to say Rashford should’ve spent more time perfecting his game and less time playing politics?”
Left-wing group Momentum said Elphicke has “consistently demonised refugees and aid groups”. It accused Sir Keir of taking Labour away from its core values.
Ex-Shadow Chancellor John McDonnell added: “I’m surprised and shocked like many people.
“I’m a great believer in the powers of conversion, but I think even this one would’ve strained the generosity of spirit of John the Baptist, quite honestly…”
Elphicke is the second Tory MP in as many weeks to defect to Labour following Dan Poulter. She was in talks for “some time”, Labour said.
In a statement, Elphicke said the Tories under Rishi Sunak had become a “byword for incompetence and division”.
The party had “abandoned” the centre ground while key pledges made by Boris Johnson in his 2019 manifesto have been “ditched”, she said.
Sir Keir side-stepped yesterday when asked if more MPs may defect before the election.