The Six Nations countries are in danger of falling out over plans to aggregate their television and commercial rights, with England and France demanding an unequal share of the proceeds to pay off their clubs.

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The Six Nations set up Project Light 18 months ago to see whether pooling everything together for their championship and autumn matches would yield a greater financial return after struggling to find sponsors. It gathered momentum after Benjamin Morel, who spent 20 years with the NBA, took over as chief executive at the end of last year.

Four investment companies, including CVC, who this year took a stake in Premiership Rugby, and IMG, have been interviewed this year. The unions would remain in control, conceding 27% equity in the business, but allow the successful bidder to take over the commercial arm, almost certainly meaning the end of the Six Nations being shown exclusively on free-to-air television.

Meetings have been going on during the championship that ended last weekend but a sticking point has been the insistence of England and France that they should receive more than the other four because they would have to buy the support of their powerful clubs.

That has left the other four questioning the value of a deal that would potentially make them more vulnerable to Premiership and Top 14 clubs when it came to holding on to their best players. Wales, the grand slam champions, are already under pressure from their squad with a new contract system being drawn up and English clubs looking to sign players such as Gareth Anscombe, the Cardiff Blues fly-half who kicked 20 points against Ireland last Saturday and created his side’s try.

The feeling was expressed in a recent meeting that Premiership Rugby was becoming increasingly bullish after its deal with CVC and that the Rugby Football Union needed to show some leadership. It is understood the RFU has been considering contingency plans should it fail to reach agreement with its clubs over the international calendar. One would even see newly formed English regional teams entering the Pro14 with players centrally contracted.

The four would stand to gain more from World Rugby’s plan to set up a Nations Championship from 2022, although Ireland, Scotland and Italy oppose the governing body’s insistence on relegation being introduced to the Six Nations and to the Rugby Championship, which would be expanded from four to six teams, even though it could take the form of a play-off and a parachute payment would be made.

World Rugby met the leading unions, together with Fiji and Japan, in Dublin last week. It initially gave them two weeks to sign a due diligence agreement, which would allow the mutual inspection of books, but that deadline has been put back until 5 April. Under the plan there would be no involvement of private investment companies and the Six Nations would remain on free-to-air television.

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The Nations Championship would also allow an equal share of revenue, before merit money, and many of the countries in the Six Nations are aware they may be trying to sell something under Project Light that they cannot deliver. If the Nations Championship fails to achieve lift-off, the international calendar would revert to the agreement reached in San Francisco two years ago.

That moved summer tours back a month to July, to allow Super Rugby to be completed, and retained the autumn internationals in November. The major southern hemisphere unions have warned that, if the Nations Championship is aborted and the European unions opt for Project Light, widening the financial gap between north and south, they would consider not beefing up their championship and not touring, unless a fee was involved.

Unions the world over need to increase their turnover, the RFU included. The Welsh Rugby Union is under immediate pressure because its players have agreed to act collectively following the regional row that blew up during the Six Nations when a proposed merger between the Scarlets and the Ospreys was publicly called off, leaving a number of players in contractual limbo, including the national captain, Alun Wyn Jones and Anscombe.

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Wales’s professional rugby board, made up of representatives from the union and the regions, met for five hours on Monday. It was agreed to end the merger idea and the regions have been given budgets for next season but hard decisions need to be made.

“Doing more of the same is not enough,” said the Dragons chairman, David Buttress, who is looking for backers to buy back control of the region from the WRU. “The game needs investment. It was unfortunate that everything got played out publicly a few weeks ago and sometimes things are more difficult than they should be, but some really exciting plans are being made.”

Meanwhile the Scarlets have announced that three of Wales’ grand slam heroes have signed new contracts. Jonathan Davies, Ken Owens and Rob Evans have all agreed new deals to extend their stay with their home region.