Six clubs have backed a Rugby Football Union proposal to replace National League One with a fully-professional Championship from next season.

RFU council members will vote tomorrow on the proposed new structure, which would see the number of clubs in the second tier of English rugby reduced from 16 to 12. The Championship would offer a route into the Anglo-Welsh Cup while promotion and relegation would be decided by extensive end-of-season play-offs.

The RFU believe the Championship is "the way forward" for English rugby. But First Division Rugby, the umbrella body for National League One clubs, questioned this week why the RFU are in a "mad rush to force through" the proposal in challenging economic times.

FDR Chairman Geoff Irvine fears the new structure would be "financial suicide" for clubs. But Coventry, Doncaster, Exeter, London Welsh, Nottingham and Plymouth Albion have written a memo to the RFU council urging them to vote in the change tomorrow.

It states, "In connection with the proposal to create a Championship league of professional rugby, following yesterday's meeting at the RFU seeking clarification of certain issues we wish to bring to your attention the following:

1. The FDR position statement which has been circulated to you by Geoff Irvine has not been put before either the FDR Board or its shareholders. The statement is selective in its content and inaccurate conclusions may be drawn from it. It does not, for example recognise:

(a) a majority vote of FDR clubs to establish a 12 club league for 2009/10
(b) the guarantee of 32 fixtures
(c) the economic benefit flowing from title sponsorship and TV coverage (incidentally, the famous 12-4 vote was not in connection with the RFU's latest proposals)

2. The statement paints a draconian financial scenario which implies instant insolvency for many clubs ("financial suicide"). It gives no recognition to the necessary development of the professional game and the fact that once implemented promotion and relegation is only one up from Level 3 and one down from Level 2. Proper financial management will therefore mean that the process will evolve over time

3 Neither the FDR Chairman nor the FDR Chief Executive has negotiated any alternative funding for 2009/10, demonstrating their lack of even short-term thinking. In theory FDR is faced with no funding if the RFU's proposals are rejected.

"We understand that the FDR Chairman is putting a proposal to you to defer the RFU proposals. This is in direct contravention of a majority vote of FDR clubs, who determined that the reduction from 16 to 12 clubs be implemented in one year."

The memo concludes: "We sincerely request your support in moving the development of level two rugby into the professional era without further delay."

Irvine responded by stating he was "amazed" the RFU had made the memo public "on behalf of a minority group of six clubs".