Ferdinand and Ennis were joined by Ade Adepitan, the wheelchair basketball player who was one of the ambassadors of London's 2012 bid, in insisting the stadium must be retained with a running track.
Tottenham are bidding against West Ham to take over the venue but Spurs' plan would see it demolished and rebuilt without a track.
Judgement day: The post-2012 occupants of the Olympic Stadium will soon be known, with bidders West Ham and Tottenham battling out
Ennis said: 'I think it would be such a shame if we lost it. I just hope the right decision is made and Britain still has that track.
'It's our Olympic Stadium and I'd love to see it used as an athletics stadium in years to come - it would be strange if it was just a football ground.'
Outspoken: Jessica Ennis
Manchester United defender Ferdinand, who began his career at West Ham, also backed the Hammers' plan. He said: 'Arsenal have done it with Highbury, leaving their old ground and going to the Emirates, and it hasn't altered their success or what they're trying to do.
'If that could be the same for West Ham then it would be great. It's down to the powers that be at the club and there's so many things that will determine whether they go there but if it's good for the club then great.'
The issue of playing football inside a running track has been the main bone of contention in the debate over the future tenants but former player Paolo Di Canio claimed that should not weigh against the Hammers.
He said: 'Having played at the Stadio Olimpico in Rome for Lazio which also has a running track, the atmosphere has always been fantastic. I am certain the passion of the West Ham supporters will create just as much of an amazing atmosphere at the Olympic Stadium in Stratford as they do at Upton Park.'
Adepitan was among the London 2012 delegation in Singapore in 2005 that promised there would be an athletics legacy in the stadium after the Games, and he said that pledge should be honoured.
Powerful voice: Manchester United and England star Rio Ferdinand (right)
He said: 'It is a fantastic stadium the way they have set it out, the seats are so close to the action. The atmosphere will be amazing [for football] but I still hope that we can follow the Olympic ethos and give respect to the Olympic and Paralympic sports.'
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Explore more:People: Jessica Ennis, Rio Ferdinand Places: London, Rome, United Kingdom, Singapore, Olympic Stadium