Middlesex have become the first county to publicly declare opposition to the ECB's move to change its constitution in order to pave the way for a new, eight-team T20 tournament.

The ECB proposed amending its Articles of Association last month, in order to remove the stipulation that any new competition had to involve all 18 counties. Letters were sent to the ECB's 41 constituent members (the first-class counties, MCC, Minor Counties Cricket Association and 21 recreational boards), with 31 positive responses needed to pass the change.

Colin Graves, the ECB chairman, called it a "watershed" moment for the game that would help to attract new audiences. The counties have been promised a fee of £1.3m a year in order to compensate them for the creation of new teams to take part in the competition, scheduled for 2020.

However, while the changes to the constitution are expected to be voted through, reigning county champions Middlesex have announced that they will not be supporting the move after consultation with members at the club's AGM.

Middlesex chairman, Mike O'Farrell, said the planned tournament represented "great risk" to the club's financial position - citing their tenancy agreement with MCC to play at Lord's - and suggested that removing the requirement for all 18 counties to be involved could lead to a reduced status for some.

"Whilst Middlesex is fully supportive of the creation of a new T20 tournament to drive the future of the game, we are unable to support this proposal at the current time," O'Farrell said. "Middlesex has a unique position in playing at a ground that is likely to be a host venue at the tournament, yet not benefiting from the revenues associated with that status. Therefore, the financial impact on Middlesex is still very uncertain and contains great risks to our current revenue streams.

"Additionally, the current governance of the ECB means that this article change creates a significant risk that counties that are not host venues for the new tournament may, in the future, be downgraded both in status and in revenue terms.

"We welcome the ECB's commitment to a further revision to its articles to provide the protections that we require but, until these commitments become legally binding, we cannot support the current change of articles of association. We look forward to working with the ECB in the near future to developing a proposal that alleviates our concerns and provides a solution to domestic cricket that meets all our collective objectives."

Several counties have expressed reservations about the ECB proposals - Middlesex's London neighbours Surrey foremost among them - but it is not known how many are prepared to oppose them. Yorkshire, Sussex, Somerset, Leicestershire and Derbyshire have come out in favour. Replies must be received by the ECB within 28 days of the letters being sent out, with a non-response effectively a vote against.