The countries included those that signed a similar declaration last November plus Poland - the EU's largest new member state with a significant sugar industry and an influential voice under the bloc's complex voting system.
"Our proposals are rooted in our shared objective to keep a viable sugar sector in all signatory member states," read the letter sent to EU Agriculture Commissioner Mariann Fischer Boel.
"It would be unacceptable to dismantle the production in certain regions and at the same time increase it in others," said the letter, obtained by Reuters. It also called for more flexibility at national level in implementing proposals.
All 11 countries fear huge job losses and the disappearance of their national industries due to the steep cuts planned for the EU's internal sugar and beet prices, as well as the inevitable falls in production and exports.
EU sugar policy, widely criticised for distorting global trade and harming Third World farmers by stimulating excess production, has barely changed since the late 1960s and inflates EU sugar prices to more than three times the world market.
While Third World countries and free trade campaigners say the plans do not go far enough to prise open a highly protected market, some of Europe smaller producers say the result would be a flood of imports as their own industries go bust.
If production cuts were needed at all, the letter said, they should be applied first to regions with a surplus and the idea of a one-million-tonne increase in surplus C-sugar, which must be exported without subsidy, was unacceptable.
France and Germany are the EU's biggest producers of C-sugar, followed by Poland and Britain.
The first letter sent by these states, whose combined voting weight can block a decision on sugar reform, was authored by a group of Mediterranean countries led by Italy and Spain. Finland and Ireland also signed the letter. The other signatories to the letter were Greece, Hungary, Latvia, Lithuania, Slovenia and Portugal.
EU agriculture ministers aim to reach an agreement on the Commission's reform proposal at a meeting late next month.
For those countries where the production loss was highest, the EU should provide additional compensation, the letter said.
It also hinted that the 11 countries would favour "partial decoupling" of sugar subsidies, meaning that a certain amount of cash would remain linked to the amount of production - a concept first floated in the EU's mammoth 2003 farm reform. At present, the Commission wants a complete break of this link, with no sugar payments tied to output. This could now become a bargaining chip for the November meeting.