The government has "ruled out" axing GCSEs in favour of a two-tier system, Education Secretary Michael Gove has said.
On Thursday, reports in the Daily Mail suggested Mr Gove was preparing to replace GCSEs in England from autumn 2014 with O-levels and bring in a simpler, CSE-type exam for less academic teenagers.
But as MPs took part in an opposition-led debate on 26 June 2012, the education secretary repeatedly refused to confirm that the story was accurate.
He said a consultation on the subject, expected in the next two months, would set out ways to "improve GCSEs and get world-class qualifications".
"We need higher aspirations for all students," he said.
"I've ruled out any two-tier system, I want a one-tier system... we will have one qualification for all pupils."
Opening the debate, shadow education secretary Stephen Twigg criticised the timing of last week's reports.
"These proposals were leaked just as pupils were sitting their GCSEs," said Mr Twigg.
"As nervous and stressed young people were queuing up to sit hugely important exams, the secretary of state was saying they were worthless - how insulting.
"How insulting to young people who had studied and revised so hard."
He urged the House to back a motion arguing that the proposals "could, in the words of the deputy prime minister, 'lead to a two tier system where children at quite a young age are somehow cast on a scrap heap'".
But MPs rejected Labour's motion by 298 votes to 222, a government majority of 76.
They agreed instead, by a similar margin, to a government amendment welcoming "the opportunity to address the weaknesses of the system introduced by the previous administration, which undermined confidence in standards, increased inequality and led to a reduction in the take-up of core subjects such as modern languages, history, geography and the sciences".
There are 20 opposition days allotted in each Parliamentary session. This is the third allotted day of opposition debate in this session.