Liberal Democrat leader Tim Farron pledged to scrap Sats tests as he branded the education system as having become a “quality assurance industry”.
Mr Farron also condemned the government’s plans to expand the number of grammar schools across the country.
In his keynote speech at the Lib Dems annual conference in Brighton, the MP for Kendall said primary schools were no longer focused on developing children “for later life, for work, or for further study” but on testing.
“It's not about whether kids can solve problems, or converse in other languages - or even their own. It's about statistics. Measurements. League tables.
“Instead of building an education system, we have built a quality assurance industry,” he told delegates.
He said he wanted schools to be places where teachers were free to teach “not just pass exams”.
“So I want to end the current system of Sats in primary schools that are a distraction from the real education that professional teachers want to give their children; that weigh heavy on children as young as six and add nothing to the breadth of their learning,” he said.
He then went on to criticise the Conservatives’ plan to expand selective education.
“What are we doing, in 2016, threatening to relegate 80 per cent of our children to education’s second division by returning to the 11-plus? Every parent wants to send their kids to a good school. But more selective schools are not the answer,” he added.