Sir Patrick Moore, the astronomer, this week called for text books to be rewritten to show eight, not nine, planets in the solar system.
His comments came as the International Astronomical Union (IAU) was considering whether there are in fact 12 planets, following a debate over the status of Pluto in the solar system.
Whatever the outcome of the deliberations, publishers could lose million of pounds reprinting books with the latest information.
Sir Patrick, who presented The Sky at Night on the BBC for more than 40 years, said: "It's perfectly obvious. Pluto is not a planet in the way Mercury or Venus are. It was only discovered in about 1930 and we thought it was much larger than it is."
He said a planet was broadly defined as a spherical body with a solid or gaseous surface, measuring more than 3,000 miles in diameter and which travels around the sun. Pluto measures just 1,467 miles. "Textbooks should be reprinted. There are eight planets, not nine," Sir Patrick said. The eight he says are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
However, the IAU, of which he is a member, will next week decide whether there are 12 planets in the solar system.
It follows the discovery of several planet-like objects including Ceres, the largest object in an asteroid belt between Mars and Jupiter; Pluto's moon Charon and now Xena, a 1,864 mile-wide object found on the edge of the solar system, known as the Kuiper Belt.
Members will vote on a new definition for planets, which would include the eight classic planets as defined by Sir Patrick and "Plutons" which are different because they take longer than 200 years to orbit the sun and their orbits are highly tilted and non-circular.
Plutons would include Pluto, Ceres and Xena.
Graham Taylor, director of the Educational Publishers' Council, said: "If there is a significant change in the definition of what is a planet and what represents the solar system every science text book will have to be amended as soon as possible."
He said text books were updated each year but if an immediate change was made existing stock would have to be scrapped costing publishers millions of pounds.
He estimated the secondary science textbook market alone was worth about Pounds 10 to pound;15 million and that publishers could stand to lose at least 25 per cent of the cover price of each book if they were forced to reprint books.
Dr Derek Bell, chief executive of the Association of Science Education, said schools and exam boards would need to carefully consider syllabuses relating to space and the solar system if the IAU agrees the change.
He said: "You can't ask a simple question like 'how many planets are in the solar system?' and then penalise a child for saying nine."
However, he added: "This is a good illustration that science knowledge is not static. It changes. I think the debate, including Patrick Moore's argument, is going to go on for a little bit longer before the science community fully accepts it."
Sir Patrick maintained there were only eight planets in the "accepted sense" and said the new discoveries should not be classified as planets.