The number of couples entering civil partnerships in Portsmouth has gone down for the third year in a row.
A total of 52 couples took part in civil partnership ceremonies in 2012.
The decrease is likely to have resulted from the introduction of marriages for same sex couples in March 2014.
The report, which was published on Thursday, shows there were 861 civil partnerships formed in England and Wales last year - down 49 per centr from 2014.
Elizabeth McLaren, from ONS, said: ‘Civil partnerships have fallen sharply since the introduction of marriages for same sex couples in March 2014.
‘On the other hand, civil partnership dissolutions have increased due to the rising number of civil partnerships that were formed since they were introduced in December 2005.
‘Dissolutions are likely to reduce in the future as more same sex couples form marriages instead of civil partnerships.’