Harlequins are planning a new 25,000-capacity stadium on the site of Twickenham Stoop HENRY BROWNE/GETTY IMAGES

Harlequins are planning to build a 25,000-capacity stadium on the site of Twickenham Stoop in an ambitious project expected to cost around £50 million.

The existing 14,800-seat stadium has been operating at 98 per cent capacity in recent years and the Aviva Premiership club’s vision is to develop a new multi-sport facility, with strong consideration being given to an artificial pitch to ensure that it can be used all year.

Quins will also look to uncover and resurface the cinder running track that was home to Richmond and Twickenham Athletics Club until 1984, but is now a concrete walkway that runs around the field.

Final facilities will be determined during a six-month consultation period, starting in January, with local residents and businesses invited to offer…