Less than one in four teachers are in favour of the government's plans to scrap GCSEs and replace them with a new English Baccalaureate Certificate, a poll suggests.
It also reveals that many teachers do not think qualifications should be tested simply through a final exam.
Instead, the majority believe students should sit a mix of exams and coursework conducted under strict supervision.
The YouGov Teacher Track survey, questioned almost 1,000 UK teachers about the government's proposals to reform the exams system in England.
Ministers' plans to replace GCSEs in the core subjects in England with a new exam called the English Baccalaureate Certificate (EBacc) were revealed last month.
The courses would be first taught from September 2015, with the first exams taken at the end of the courses in 2017.
The survey found that 23% of the teachers questioned back the EBacc proposals, while 48% oppose them. The rest said they did not know.
It reveals that 73% believe that the GCSE marking system should remain the same, with pupils graded on a mixture of final exams and "controlled assessment" - coursework carried out under strict classroom supervision.
Just under a quarter (24%) thought it should be changed to marks based only on final exams.
The poll also found that three quarters of teachers (76%) are in favour of proposals to allow only one exam board for each subject.
YouGov associate director Ian Neale said: "The results of this survey clearly show that at the moment Michael Gove has a steep hill to climb in terms of getting teachers onside with his vision of the exam system.
"While it would appear the public are basically on the fence about 'Gove levels', teachers are on the frontline of education in England, so their fairly decisive opposition to the reforms could be problematic for the Government in pushing through real change. There is some convincing to be done."
The poll comes a week after England's exams regulator indicated she may have concerns about the Government's proposed timetable for introducing the EBacc.
Glenys Stacey said that Ofqual needed to understand more about the detail of the planned curriculum so that it could shape the qualifications.
She told a conference in Belfast that Ofqual will advise the Government on its timetable and "will say if it is not achievable, or if the risks to standards or delivery are unacceptable."
She added: "Is the timetable achievable?
"Well, we are not saying at the moment that we have come to a view that it is not possible to achieve it, but there is frankly a lot to understand and work to be done in the coming months to evaluate that."
The YouGov poll questioned 832 UK teaching professionals online between September 21-27.
A Department for Education spokesman said: "This survey shows that teachers are clear that retaining the GCSE status quo is simply not an option - more than three-quarters want the system changed so that all children take a single exam for each subject.
"Modules, coursework and controlled assessment have all undermined the credibility of GCSEs by narrowing the curriculum, encouraging teaching to the test and fuelling grade inflation. And only last month headteachers highlighted the problems with the current marking system.
"There must be change. The new EBCs will be robust, rigorous and relevant - and will match exams in the world's best education systems."