The number of GCSEs awarded declined for five consecutive years under Labour, according to figures released by examinations watchdog Ofqual.
Over the same period, between 2005-6 and 2009-10, the number of young people completing 'other qualifications' rose by more than 2 million.
Many of these 'other qualifications' were recently described by Professor Alison Wolf in an independent review conducted for the government as 'low-level vocational qualifications, most of which have little to no labour market value'.
The figures reinforce a damning picture of how educational standards plummeted under Labour with young people pushed away from core subjects - an issue that Education Secretary Michael Gove is addressing by introducing the 'English Baccalaureate'.
The English Baccalaureate is a new certificate which rewards pupils who have secured a C grade or better across a core of academic subjects - English, mathematics, history or geography, the sciences and a language. The percentage of children achieving the English Baccalaureate in each school is now also provided in Performance tables.
Conservative MP Nadhim Zahawi said:
"This is further proof that the last government placed propaganda about rising examination success rates ahead of the importance of ensuring pupils take high-quality qualifications. They let down a generation of young people.
"Under this government, the English Baccalaureate will ensure that all pupils, whatever their background, can access a rigorous, broad-based and academic education."