However, a takeover has not been ruled out.
But Ted Wragg, professor of education at Exeter University, wants an explanation from ministers after the link was reported at the weekend. He said: "This is the first time it has been suggested that an exam board should be privatised.
"There has been no debate about whether we should have a privatised exam board rather than a public service one. This would create a situation where you have a private publisher which would know in advance what is going to go in a syllabus and in exams because it is a board. It gives them a commercial edge."
Neither Edexcel nor Pearson would comment on the reports, which suggest a deal could be signed before the end of the month. However, as The TES has reported, the board wants to introduce a system of on-line marking.
Frank Wingate, head of external relations at Edexcel, said it would take millions of pounds to fully update its systems. Edexcel, which has an annual turnover of pound;100 million, has been making losses or breaking even for the past few years.
Mr Wingate said: "We have been making it clear for 18 months that we think more investment is important. We want to modernise the examination system."
The Department for Education and Skills referred press calls to the Qualifications and Curriculum Authority. A spokeswoman said: "The acquisition of exam boards is entirely up to the QCA. Any discussions would have taken place between the QCA and Pearson."
The QCA said that when it accredited qualifications, it did not consider the issue of the ownership of an exam board