The chairmen of Garstang and Great Eccleston shows, Tom Ibison and Alistair Parkinson, have sent jointly written letters to the monarch in her role as Duke of Lancaster, and the Prince of Wales, to outline their concerns.
The royal plea comes at a time when Garstang Show is already facing a cash crisis after the foot and mouth scare forced the last-minute cancellation of livestock classes at this year's show, which was also hit by poor weather and lower than usual attendance.
It is understood the letters, due to arrive at Buckingham Palace and Highgrove House today, spell out how all three shows may suffer from lower attendances if the Royal Lancashire Show re-locates to land owned by the Queen at Myerscough.
Garstang Show secretary Sue White confirmed the letter was a "plea", adding: "We feel passionately about our shows. Another show in the area is looking a realistic possibility, but three shows within seven miles of each other within four weeks during the summer is a big concern."
Mrs White also revealed details of the cash crisis being faced by Garstang Show following this August's slump in attendance.
She said the eve-of-show cancellations of cattle, sheep and goat classes due to foot and mouth movement restrictions, along with poor weather, had led to around 8,000 people attending rather than the 12,000 figure of 2006.
The drop in numbers has cost the show an estimated £20,000.
Mrs White said the show would be in the red when the accounts were prepared and it was already facing cash flow problems.
On the issue of the Royal Lancs show concerns, she said individual members of Garstang and Great Eccleston agricultural societies had been urged to make their concerns known to Wyre Council, whose deadline for receiving comments on the Duchy plan comes to an end today (Wednesday, November 28).
Responding, a Duchy spokeswoman said: "We do not see the proposed Duke of Lancaster Park as being in direct competition with other local shows. We believe our masterplan will help to promote rural pursuits to a much wider audience."
The farm show leaders' Royal lobbying has come at the same time as opponents of the Royal Lancs plans are stepping up their campaign.
No2DuchyPark.org spokeswoman Lesley Sumner said residential and business campaigners opposing the proposal would be placing prominent posters in their gardens and properties on the A6 this week.
She said the campaign group's supporters had delivered 2,500 leaflets at Broughton, Barton, Bilsborrow, Myerscough, as well as in Great Eccleston and St Michaels, villages along the 'alternative/contingency' traffic route from Preston to the proposed Myerscough showground.
Preston's planning committee is due to consider its opinion on the plans on Monday (December 3). Its opinion has been sought as a neighbouring council. The original agenda for the meeting, published last week, urged no objection.
That recommendation prompted anger among opponents of the plans, including several rural Preston Conservative councillors, after Preston's Tory council leader Coun Ken Hudson told a public meeting in Barton last month Preston WOULD oppose the plans.
As The Courier went to press it was learned that officials would now be changing their recommendation to "Object, unless certain conditions are fulfilled."
A council spokesman said the reason for the change in the recommendation was "in the light of public feeling", and that the new agenda would be made public later this week.
Coun Hudson said he would be attending Monday's meeting to stress "the serious concerns of local residents and parish councils about the traffic chaos that will ensue if this planning application is approved by Wyre Council."
A Wyre spokesman confirmed today was the deadline for comments on the plans, but added comments would be accepted up to the day of the meeting.
Wyre planning committee will decide the plans at their meeting on January 2 or February 6.

* Garstang Agricultural Society is to host a race night at Garstang Country Hotel and Golf Club on the evening of February 8 in an effort to raise cash for society funds and help boost the show's balances. Officials hope several thousand pounds will be raised. For further details contact Sue White on 01253 790997.