Labour’s Angela Rayner led a stinging attack against the government’s plans to expand the number of grammars this afternoon, stating the Green Paper consulting on the proposals was a “waste of money”.
The shadow education secretary also taunted her opposite number by claiming that ministers have been unable to produce any evidence supporting their proposals to establish more selective schools.
But education secretary Justine Greening hit back at Ms Rayner for opposing a "consultation document that looks at how we can reform grammar schools".
Speaking in the House of Commons during education questions, Ms Rayner demanded to know how much money had been spent “trying to find any facts to support their policy of segregated schools”.
“Spending public money on a policy without evidential basis is simply wasting it. When the secretary of state last came to the House she couldn’t cite any evidence that this policy would boost social mobility. Has she found any since?” Ms Rayner added.
Last week, prime minister Theresa May vowed to establish the first new grammar schools for 50 years at the Conservative party conference.
And in the Commons this afternoon, Ms Green defended the policy, which is currently being consulted on.
“A lot of what [Ms Rayner] said is incorrect; she will be well aware of research put out by the Sutton Trust that clearly set out the increased attainment of free school meals pupils in grammar schools,” the education secretary said.
“It’s totally untenable to set out her concerns on grammars while being opposed to any kind of consultation document that looks at how we can reform grammar schools.
"We do want to reform grammar schools and it is now right to look at what role grammars can play in the 21st century."
The government's grammar school plans were boosted this afternoon as Northern Ireland's largest party signalled its support.
Sammy Wilson, the Democratic Unionist Party's education spokesman, urged the Prime Minister to ignore the "barrage of criticism" aimed at her desire to roll out a new generation of selective schools.
He added that two-thirds of people canvassed on grammar schools back an extension as he sought assurances from Ms Greening that she will not be deterred by the "siren voices" of those who oppose them.
The Government believes new grammar schools will help give pupils from poorer backgrounds the same academic opportunities as their richer counterparts, but Tory MPs are among those who have voiced opposition to the idea.
As Ms May's administration has a slender majority in the Commons, only a handful of her MPs voting against the proposals could scupper them.
Support from the DUP's eight MPs would strengthen the Government's hand when it comes to parliamentary votes, with First Minister of Northern Ireland Arlene Foster acknowledging last week that there are "some synergies" between the DUP and the Tories.
Ms Foster and DUP representatives have already met Mrs May amid speculation about the level of support the party will give the Tories in the Commons.
Speaking during education question time, Mr Wilson dropped further hints about where the DUP's loyalties lie on grammar schools.
He asked Ms Greening: "Are you encouraged that of those who have been canvassed on the issue, two-thirds are supportive of the Prime Minister's policy of increasing social mobility for those from poorer backgrounds through the provision of increased grammar schools?
"And will you give an assurance that you will not be deterred by the siren voices or the barrage of criticism of this policy by those who are ideologically opposed to the policy even though they benefited from grammar school education themselves?"
Ms Greening replied: "You set out the situation very clearly and as you point out, for children on free school meals in particular, grammars are able to close the attainment gap because the progress those children make is double those of their better-off classmates.
"Now (Labour) wants to close that opportunity down, we want to level it up. That's the difference."