Tristram Hunt, Labour's shadow education secretary, has provoked a social media firestorm after telling a parent and a teachers' group to "stop moaning" and "do some work".
Thomas Mann, a father of two, asked Hunt on Twitter to direct him towards details of Labour's education policies.
However, after being given the link, Mann was unsatisfied with the "soundbites" on the party's website and asked for more specifics. In response. Hunt told him, and the anti-coalition protest group "Teacher Roar", to go and "read the speeches", adding: "Your industry will be rewarded".
The response, provoked an onslaught of shocked tweets, as users rounded on his "patronising" message.
The Tories also joined in the mockery, with civil society minister Rob Wilson calling it "lofty patrician advice".
Mann later said he felt "condescended" by the Labour frontbencher and treated "like a little person".
"I think politicians have lost the idea of who their employers really are and who they are meant to serve," he told Politics.co.uk.
The spat will be deeply unhelpful for the party in its attempts to woo teachers and parents, as a new poll found that its lead among voters over education has disappeared.
According to a survey by ComRes/ITV, the Tories now enjoy a one point lead on which party voters trust most to improve the education system.
Another poll, by YouGov, found that Labour had a clear lead among teachers, with 57% backing the party as opposed to just 16% backing the Tories.
Both Labour and the Tories are trying to prove they have the best policies on education. David Cameron has announced a "war on mediocrity" by unveiling plans to sack headteachers at coasting schools.
Any English school assessed as requiring improvement by Ofsted will be put under new leadership unless it can show it has plans in place to bring about rapid change, he will reveal in a speech in London.
Cameron said: "As parents we're hardwired to want the best for our kids. No one wants their child to go to a failing school - and no one wants to them to go to a coasting school either.
Read more on General Election 2015
"So this party is clear. Just enough is not good enough. That means no more sink schools - and no more 'bog standard' schools either. We're waging an all-out war on mediocrity, and our aim is this: the best start in life for every child, wherever they're from - no excuses."
In a statement that did not provoke outrage on Twitter, Labour's Tristram Hunt said: “David Cameron’s flawed schools policy is damaging our education system and failing to close the learning gap between disadvantaged children and the rest.
“The surest way to raise standards in every lesson, in every school, is to improve the quality of teaching in the classroom. That begins with an end to Cameron’s unqualified teachers policy. Labour will ensure that all teachers are qualified and continue to train to improve their teaching as a condition to remaining in the classroom. This is how we improve the learning and life chances for all children and raise our international position in reading, writing and maths.”