
Circulation for the venerable title slipped 3.21% month on month to 331,488 in March, its first complete month
The Observer's circulation also declined 23.09% year on year, the biggest fall among the Sunday papers, although this includes 22,737 bulk copies stripped out by the publisher earlier this year.
It was the worst performing Sunday newspaper in England.
Meanwhile, News International's Sunday newspaper News of the World continues to lag behind its weekday sister title The Sun, with a circulation of fewer than three million copies a week.
The News of the World had an average circulation of 2.9 million during March, down 2.98% month on month, and 3.71% year on year.
The second biggest Sunday newspaper remains Associated Newspapers' The Mail on Sunday, with a circulation of 1.95 million, down 1.29% month on month and 2.22% year on year.
Rupert Murdoch's broadsheet The Sunday Times' circulation was 1.11 million, down 0.94% month on month and 10.38% year on year.
The average circulation of Trinity Mirror's Sunday Mirror was 1.15 million, down 0.75% month on month and 6.64% year on year.
The completion of the sale of the Independent titles to Alexander Lebedev is expected in May. The Independent on Sunday continued its decline in March, with an average circulation of 154,285, down 0.88% month on month and 8.03% year on year.
The average circulation of Trinity Mirror's Sunday Mirror was 1.15 million, down 0.75% month on month and 6.64% year on year.
The completion of the sale of the Independent titles to Alexander Lebedev is expected in May. The Independent on Sunday continued its decline in March with an average circulation of 154,285, down 0.88% month on month and 8.03% year on year.