Some academy chains have been guilty of "empire building" rather than ensuring their schools were providing a good education, Ofsted chief Sir Michael Wilshaw has said.
He suggested that a number of executive headteachers of multi-academy trusts had been too focused on showing off how many schools they had, rather than standards.
His comments came in response to a question posed by the Commons education select committee on whether trusts had been had been allowed to expand too quickly, over too wide an area.
Some multi-academy trusts "have been allowed to grow to far too quickly, without the capacity to improve their individual schools", Sir Michael told the cross-party group of MPs.
"There was a lot of empire building going on and executive headteachers who wanted to show how many schools they had rather than whether they were any good or not," he said.
National Schools Commissioner Sir David Carter agreed that expansion had sometimes been too quick
"I think in some cases that's been a factor in under-performance, not in every one. We need to be careful we do not equate size and rapid growth with failure. I think there's examples where we can do that," he said.
He added that with the number of academies and academy chains set to drastically grow following Government reforms, he wanted to propose a structure that will allow sensible expansion.