Tanzania and Zambia have submitted proposals to the Convention on International Trade in Endangered Species (Cites), which meets later this week in Qatar, to downlist elephants from the highest level of protection.

They also want to be allowed one-off sales of their legally-held stockpiles of ivory.

But conservation campaigners are concerned that any weakening of the rules preventing international trade in elephants or elephant products could encourage more poaching and illegal trade.

The last one-off ivory sale permitted by Cites was in 2008 when Botswana, Namibia, South Africa and Zimbabwe were permitted to sell their stockpiles.

It is suggested legal sales depress the price of ivory and therefore reduce poaching pressure on elephants. But the Environmental Investigation Agency (EIA) said that, in the wake of the 2008 sale, there was a global surge in the levels of seizures of illegal ivory.

Conservationists are concerned that the legal sales give cover to illegal trade and stimulate demand for ivory among consumers.

The EIA also said investigation showed a booming illegal business in the two countries asking for the downlisting of elephants from Appendix I, where international trade is banned, to Appendix II, where ivory could be sold if Cites gives the sale the go-ahead.

In Tanzania, protected areas are subject to poaching while ivory was offered for sale to EIA investigators. In Zambia, the agency found that ivory was easily obtainable.

EIA executive director Mary Rice said: "Every new sale or downlisting is sending out another conflicting and confusing message to the effect it is acceptable to deal in ivory."