By John Ngahyoma BBC, Dar es Salaam

Tanzania's opposition is worried that life expectancy is declining

As Tanzania prepares for its general election next year, some opposition parties want the minimum voting age to be lowered from 18 years to 15.

A coalition of opposition parties in the country said most teenagers in the country complete primary school at the age of 15 when they are already politically aware.

The chairman of the coalition, James Mbatia, told the BBC that the marriage law in the country allows girls to be married at the age of 15 and some of them even have their first babies before that age.

Lowering the age will bring more chaos to an already confused political set up in Africa Don, Nigeria Have your say

In addition the opposition wants the minimum age for parliamentary candidates to be reduced from 21 to 18; and that of a presidential candidate to be lowered to 35 from 45.

The opposition leaders are concerned that average life expectancy in Tanzania has declined from 52 to about 48 years.

According to Mr Mbatia, the only way to allow people a longer stay in active politics is by lowering their eligibility age.

Important matters

However, the main opposition party, Civic United Front (CUF) - which is not part of the coalition - is against the proposal.

CUF's director of information and publicity, Richard Hiza said it was not wise to include young people in such important matters as voting.

Government insists on leaving the voting age at 18

"I still think the mature age should remain 18 and opposition parties should continue to strive to sensitise participation in political issues instead of seeking shortcuts."

The secretary general of the ruling CCM party, Philip Mangula, said they have no problem with the current voting age of 18.

"As a party we have not discussed the issue to have a stand, but I think 18 is the age one is considered as an adult, he/she is even required to pay tax at that age."