London Irish will return to the English capital in 2020 following the completion of a deal with Championship football club Brentford that will see the rugby union team move to its new stadium.

London Irish currently compete in the Championship, the second tier of domestic club rugby, and has played at Madejski Stadium, home of Brentford’s fellow Championship team Reading, for the past two decades.

Brentford Community Stadium is currently under construction and London Irish has agreed a lease deal to move in as the secondary tenant for the 2020-21 season. The club had held an agreement to play at Madejski Stadium through to 2025-26, but a break clause has been exercised to leave this deal early.

Terms of the new long-term deal were not disclosed, but Brentford will retain primacy of use at its new home. Construction on the 17,250-seat stadium and associated development commenced in April with the club’s development partner EcoWorld London, and its stadium subcontractor Buckingham Group, and is said to be progressing well.

Brentford had initially hoped to move into the new ground in December 2019 but in August confirmed that it will play a full final season at Griffin Park, its home since 1904, in 2019-20. The decision was made in consideration of “normal delays and problems” that arise with large-scale building works adjacent to railway lines. The club also pointed to the operational challenges that surround a mid-season stadium move as a reason for moving during the off season.

The Brentford Community Stadium development is intended to become an important part of the wider regeneration of the Brentford East area of West London. It will deliver a stadium together with more than 900 new homes, a new purpose-built location for Brentford FC Community Sports Trust, and a public square with shops and cafes.

In recent years, London Irish has been considering various stadium options and locations across London, initially being granted a licence to play at the new Brentford stadium by Hounslow Borough Council in February 2017.

London Irish owner and president Mick Crossan said: “In moving to the Brentford Community Stadium we feel confident that we will be able to attract a larger supporter base to join us as we build for the future, reaching out to our previous west London catchment area, to Greater London and the Irish diaspora throughout the UK.

“The stadium will be an outstanding venue. It is the right size in a great location and will provide a superb match-day experience for our supporters and sponsors alike. We’re looking forward to recapturing the special atmosphere and all-day experience we had at The Avenue, where ‘The Craic’ was born.

“The fantastic facilities at Brentford Community Stadium will complement our unrivalled training base at Hazelwood, which is the spiritual home of the whole London Irish family all the way from the minis and juniors in the amateur club up to the professional team, and having the two within easy reach of each other was a significant part of our decision-making process.

“The excellent transport links will mean that our existing and new supporters alike will find the stadium very accessible. We will be working hard with our existing supporters including all those based in the Thames Valley to highlight the various routes into the Brentford/Kew area given the adjacent M4 and existing train and Underground services, as well as the new Crossrail connection which opens in 2019 linking Reading into west London.”

Cliff Crown, Brentford chairman, added: “We are building a high-quality stadium fully equipped and ready from day one for the rigours and demands of both Premier League football and Premiership rugby. Like us, London Irish has a long history in the area and prides itself on having strong roots in the local community. We look forward to continuing to work with them over the coming months to support their successful return to the capital.

“It was always planned that the stadium would host rugby and we have been working on ensuring we have a top-of-the range pitch so both sports can be played. We believe that the deal with London Irish is a good one for Brentford FC both in terms of the fit between our clubs and the financial contribution that will help us to strengthen our on-pitch performance.”

London Irish has mainly held Premiership status since its formation in 1996-97, but was relegated from the top tier last season. However, the club currently sits four points clear at the top of the Championship table.