Pupils taking this year's GCSE science exams were awarded marks for simply being able to name an illegal drug.
And those taking languages were allowed to take a cue card to prompt them in their oral tests.
The latest revelations are sure to intensify the debate over the 'dumbing down' of the exam system.
Watchdog Ofqual revealed in March that rigorous science standards had been compromised by reforms to the exams in
But it warned improvements towards a more acceptable standard will be gradual and that this year's results will still be tainted.
Science exams were changed to make the subject more 'relevant' to teenagers, but Ofqual said some questions were no longer challenging enough.
Now an analysis of this year's papers has renewed criticism that some questions are not a sufficient test of pupils' knowledge, particularly in the sciences.
One chemistry question asked candidates, for two marks, to give an example of 'a legal recreational drug' and 'an illegal recreational drug'.
Meanwhile, a physics question asked what uses there were for microwave energy, other than in mobile phones
It comes just days before more than 500,000 teenagers across the country discover their GCSE results.
The Conservative schools spokesman Michael Gove said: 'Since the last curriculum changed, experts have warned that science GCSE is no longer as rigorous as it should be.
'We have seen questions that are not a proper test of scientific reasoning crop up in exam paper after exam paper.
'It's important we keep up with other nations that are pulling ahead in maths and science and making sure that our students sit exams that properly stretch and test them.'
The Mail revealed last month that eminent scientific bodies which investigated science GCSEs had found there are questions that have 'no relation to science' and that vital maths is 'woefully represented' in question papers.
The questions emerged in an analysis by the Tories as they announced plans to create an online library of exam papers from past years.
Their findings also reveal how pupils are not required to commit key scientific formulae to memory. This year's GCSE physics paper supplied a list of basic equations to help pupils with calculations, whereas those taking the International GCSE were expected to have learned the formulae by heart.
Elsewhere, candidates were allowed to take a cue card with up to five headings into modern language oral examinations.
There was no literature or extensive translation in modern language GCSEs to test the extent of their fluency. The archive also shows that the 2009 biology exam contains papers as short as 45 minutes.
By contrast, the IGCSEs, which are increasingly offered by private schools, are typically one hour and 15 minutes long.
Multiple choice questions appear in the physics GCSE, but not in the IGCSE.
Only one in four students passes 'core subjects'
Almost half a million 16-year-olds a year fail to achieve five GCSE passes that include the core subjects of English, maths, science and a language, it has emerged.
Fewer than a quarter finish compulsory schooling with the basic set of qualifications - down from nearly a third in 2001.
Tory spokesman Nick Gibb said: 'These are the core academic subjects that are highly valued by universities and employers. The fact that the number of children-attaining these GCSEs has fallen year on year since 2001 is a terrible indictment of the Government's record.'
The figures, obtained by the Conservatives, showed the proportion with five passes fell from 30.4 per cent in 2001 to 23.7 per cent last year.
GCSE results released on Thursday are expected to show yet another set of record-breaking performances. Pupils are predicted to pass one in five exams at A* or A.