Manchester United have been told they will have to move out of Old Trafford to realise their vision of making the Theatre of Dreams a rival to Wembley Stadium.

The Premier League giants want to increase their stadium capacity to just shy of 90,000.

United have plans to add an extra tier to the Sir Bobby Charlton Stand, which would boost attendance from 76,000 to 88,000.

Red Devils managing director Richard Arnold says they would have to become “homeless” to do it and they cannot find anywhere to go.

Speaking about the Old Trafford redevelopment plans, Arnold told the South China Morning Post: “We haven’t left the easiest stand until last. The Sir Bobby Charlton Stand is the last unexpanded stand.

“There’s not much space on either side of the stand meaning that it’s a very complex engineering challenge.

“It would be a multi-season challenge and it isn’t certain there’s a way of doing it which doesn’t render us homeless.

“We have the biggest fanbase in the country and we’re not in London, where we could use Wembley.

“So that’s not a light challenge and we don’t want to give up the home advantage we have here.”

Arnold says he can see plans coming to fruition “one day” and claims owners, the Glazers, “are 100 per cent aligned in terms of the continuing development of the stadium”.

United boss Jose Mourinho may be more interested in Arnold’s ongoing commitment to look at ways to introduce safe standing at Old Trafford.

The government this week blocked West Brom’s plans to introduce such an area at The Hawthorns.

Mourinho has moaned about a lack of atmosphere at United, so the club is likely to continue addressing the issue.

Talking to fanzine United We Stand, Arnold said: “We have pushed for it but we have to fit into the environment we’re in.

“We need to bring people with us — the local safety advisory group, police and government. We’re applying constant encouragement.”