Campaigners will hand in a letter to No 10 Downing Street later urging Prime Minister David Cameron to rethink the pace of reforms of exams in England.
Last year, Education Secretary Michael Gove announced plans to scrap GCSEs and replace them with English Baccalaureate Certificates (EBCs) from 2015.
But the campaigners fear decisions are being pushed through too quickly.
The letter is signed by 100 groups and individuals from the worlds of education, the arts and industry.
They include the National Union of Teachers; National Association of Head Teachers; Nicholas Hytner, artistic director of the National Theatre; Sandy Nairne, director of the National Portrait Gallery; Caroline Miller, director of Dance UK; campaigner Peter Tatchell; and Rosemary Johnson, executive director of the Royal Philharmonic Society.
Under the government's proposals the first EBCs, in English, maths and science, will be introduced in September 2015, with the first exams taken in 2017.
EBCs in history, geography and languages will be introduced at a later date. GCSEs, or other qualifications, will remain for other subjects such as PE, drama and art.
Cultural health
The letter says: "Whilst not being opposed to the reform of the system of examinations, nor to the drive to raise standards, we are concerned that the current consultation on the introduction of English Baccalaureate Certificates is too limited and that decisions are being made too quickly.
"We need an examination system which ensures pupils receive a rigorous, broad and balanced curriculum. We do not believe the current proposals for EBCs will do that.
"By failing to give parity to high quality creative and vocational subjects, as well as sport, these reforms will jeopardise our children's education and undermine the economic and cultural health of our nation.
"We are therefore calling for the consultation period to be extended in both time and content to ensure any concerns are addressed before steps are taken to implement EBCs.
"This extended consultation should fully engage with the views of parents, students, governors, businesses, teachers, head teachers and other concerned stakeholders before any changes are made."
The letter says a small group of its signatories would welcome the opportunity to meet Mr Cameron to further explain their concerns.
