Nigeria's prisons are not considered good enough for UK prisoners
Nigeria's government says it is happy with a UK plan to help refurbish their prisons to allow Nigerians in Britain's jails to be sent back home.
A British official said investment was needed because conditions in Nigerian jails were too poor for UK prisoners.
Correspondents say such conditions would allow prisoners to block their transfer on human-rights grounds.
There are about 11,000 foreigners in British jails, including more than 800 from Nigeria.
Analysts say Nigeria's jails are seriously congested and often damage the health of prisoners.
The possibility of help from Britain was welcomed by rights groups, but they said it marked the failure of the Nigerian government to look after its own prisons.
Nigeria's Director of Public Prosecution Salihu Aliyu said it was a "positive move".
"It should be encouraged not only between Nigeria and UK but with other countries," he told the BBC.
A statement from the UK's Ministry of Justice said the deal being negotiated would allow Nigerians imprisoned in the UK and Britons imprisoned in Nigeria to serve their sentences in their own countries.
"We believe that prisoners should normally serve their sentences in their own country - freeing up prison spaces and saving the taxpayer money on enforced removals," the statement said.
The proposed deal would allow Nigerian convicts to be sent home even without their consent.