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”.

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 away from Twickenham 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 acknowledgement 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 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.