The Rugby Football Union has ditched a radical proposal to sell Twickenham and buy a 50% share of Wembley from the Football Association, the Guardian can reveal, instead focusing on £663m plans to overhaul its current stadium.

Twickenham has served as the home of English rugby since 1909 and while the RFU is formulating plans to revamp the stadium as part of its “masterplan programme”, last year the union’s board approved a recommendation to retain an option to “leave” but to “defer formal engagement with the FA”.

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Matchdays at Twickenham drive 85% of the RFU’s revenues and the stadium has in recent years been described by the RFU’s chief executive, Bill Sweeney, as “our cash cow”. As a result the RFU has been ­reluctant to stage England internationals anywhere else but moving to Wembley was part of a “reserve” option to the union’s plans to overhaul Twickenham.

The Guardian has seen the RFU’s in-depth plans for revamping Twickenham, with a window between the end of the 2027 Six Nations and the start of the following year’s championship identified as the preferred time to carry out a large section of the work with minimal disruption. It would, however, mean that Red Roses matches and the men’s team’s World Cup warm-up matches would have to be played elsewhere in that time.

The masterplan – which focuses on property, transport and user experience – also makes reference to a previous potential option to relocate to Wembley, where England have hosted one previous match, against Canada in 1992. Wales also used Wembley – which was the subject of a £900m offer by the US billionaire Shahid Khan in 2018 – as a temporary base while the Principality Stadium was being built. “The RFU is focused on continuing to develop Twickenham Stadium,” a spokesperson for the union said. “Previous considerations looking at the viability of moving to alternative sites have been rejected.”

While the RFU has calculated costs of £663m for its Twickenham overhaul, there is an acknowledgment that is unaffordable and that more pressing works will be prioritised with around £300m in financing available. The figure of £663m is considered illustrative and the intention is for the total costs to form a longer-term blueprint and for subsequent works to be carried out as and when the union has the finances.

“The events held at Twickenham generate a significant proportion of the RFU’s revenue and allow investment in the game at all levels from community to elite,” read the plans. “Beyond its role as the RFU’s most visible asset and the home of England’s national rugby teams, this makes the stadium a critical financial driver to support the growth of the game and the delivery of the RFU’s objectives for the sport from grassroots to the elite level.

“Although the RFU has made significant investment in enhancing the stadium and the site, its development has, even in recent years, been completed without an overarching long-term strategy. This piecemeal approach has resulted in inefficiencies in operations, compliance, maintenance and, crucially, the fan experience perspectives.”

The work includes renovations of each of the four stands – which would see the minimum capacity for rugby events reduced to 80,000 – as well as the stadium roof, the car parks and the RFU’s offices relocated. The intention is that the stadium would be fully operational again by 2031.

The RFU is also seeking to improve transport links due to the overreliance on Twickenham rail station and countless reports of overcrowding chaos on matchdays. Among the initiatives being assessed to improve transport to and from matches, the RFU is exploring the use of riverboat services.

Writing in the RFU’s most recent annual report, the chief financial officer, Sue Day, outlined how such an overhaul of Twickenham is necessary to “safeguard the future revenues needed to invest back into the game”. There is a concern within the RFU, however, that such lavish spending on the stadium will be seen as incongruous at a time when the professional and grassroots games need investment.

An RFU spokesperson added: “Our long-term masterplan for ­Twickenham Stadium is being developed to ensure England’s national rugby stadium stays up to date, is compliant with all relevant regulations, provides the best possible experiences for fans, and continues to generate revenue for reinvestment into the community and professional game.

“Work will be undertaken over the next 12 months to consider next stage designs and assess what interventions might take place and when within the existing stadium footprint over the next 10 years. The RFU board has not agreed any new ­redevelopment plans. However, as you would expect, all options will be thoroughly considered as part of a long-term strategy.

“As plans are further developed, the RFU board and council will be fully consulted and engaged in the due diligence and approval process, this would include any potential funding sources. As per the RFU constitution, if borrowing of over £150m was needed, council members’ views and approval would be required. We do not anticipate major stadium works starting before 2027.”