The Irish Independent claims that O'Connell is now considering an operation to solve the problem that has seriously restricted his involvement this term.
O'Connell missed all three of Ireland's autumn fixtures against South Africa, Fiji and Argentina as a result but had initially hoped to play some part in the Heineken Cup double header with Saracens this month.
He didn't feature in the first of those fixtures on Saturday night, though, and won't be available for the return clash at Vicarage Road next week either.
The latest development is a big blow for the 33-year-old second row who is hoping to make a third successive Lions tour when Warren Gatland's squad head to Australia next summer.
O'Connell has played in the last six Lions Tests against the All Blacks and Springboks and is among the favourites to challenge for a similar spot against the Wallabies in June and July of next year.
But his hopes of doing so have been hit hard in the last few months as he has played hardly any rugby since early May.
Prior to aggravating his back complaint, O'Connell sat out Ireland's summer tour of New Zealand with a knee injury he picked up in the PRO12 win over Ulster back at the back end of last season.
He returned for the European encounters with Racing Metro and Edinburgh in October but his latest setback means he hasn't featured at all for the past seven weeks.