London (AFP) - England suffered another setback in their Six Nations preparations when Joe Marler withdrew from their training squad on Tuesday following a second positive Covid-19 test in three months.

The 31-year-old Harlequins prop’s latest case was confirmed by lateral flow and PCR tests, with Marler pulling out of a 36-man training camp in Brighton.

Marler missed England’s win at home to Australia in November following an earlier positive test for the virus, but returned as a replacement for the Twickenham victory over world champions South Africa the following week.

England coach Eddie Jones has decided against calling up a replacement for Marler, capped 74 times by his country.

And given his period of self-isolation will extend into next week, there are now doubts over the experienced front row’s availability for England’s Six Nations opener against Scotland at Murrayfield on February 5.

All other players and staff in Jones’ squad have returned negative results but England are still without Owen Farrell and dashing wing Jonny May due to ankle and knee injuries respectively.

Meanwhile Courtney Lawes, who deputised as captain when fly-half/centre Farrell was sidelined in November, has been unable to train this week after the forward was ruled out with concussion.

Farrell’s ongoing absence saw George Ford recalled from international exile by Jones on Monday, with the in-form Leicester fly-half having won the last of his 77 England caps during a 32-18 Six Nations loss away to Ireland in March.

Jones named Farrell as England skipper last week, even though he has not played any rugby since suffering an ankle injury against Australia in November.

But a fresh ankle injury sustained while the 30-year-old trained with club side Saracens has ruled Farrell out of the Calcutta Cup clash against Scotland.

It appeared that Jones was planning to play Farrell at inside centre, alongside Marcus Smith at Murrayfield following the Harlequins fly-half’s impressive showing for England in November.

But the veteran Australian coach will now have to look again at his 10-12 pairing in the lead-up to the latest edition of rugby union’s oldest international fixture, with Henry Slade, Mark Atkinson, Joe Marchant and the uncapped Luke Northmore all candidates for the inside centre role.