years to come."
Mr Speck goes on to describe the group's attitude as "deplorable", in light of the announcement that Pfizers at Sandwich is to close.
In response, FPOG issued a statement saying its members were "shocked" that the park had resorted to "dirty tricks".
It added: "FPOG have always recognised the important contribution which the KSP can make to Swale's economy.
"That contribution can be achieved without massive expansion outside of the park's security fence, obliterating hundreds of acres of prime countryside.
"KSP management must withdraw their public statement accusing FPOG of campaigning to close the park and acknowledge the statement as untruthful."
Andy Hudson, spokesman for FPOG, which was set up to represent Bapchild, Bredgar, Milstead, Tunstall and Rodmersham, added: "I have absolutely no idea where they have got this from."
KSP's letter was sent to tenants just two days after the Gazette revealed a protest march had been organised by FPOG for Saturday against large scale house building plans and what it described as a "monstrous" expansion of the park.
In the letter, Mr Speck urged tenants to take part in Swale Council's consultation on future development in the borough for its Core Strategy and support the aspirations of the park to expand.
Of particular importance, he wrote, was a new link to the M2. He accused FPOG of misleading people by claiming it could only be paid for by building thousands of new homes.
FPOG said it thought the letter was an attempt to undermine the council's public consultation.
Park tenants contacted by the Gazette were remaining tight-lipped, while the park's management declined to comment.
The FPOG march is due to set off from the Wilkinson end of Sittingbourne High Street at 10.30am on Saturday.
Mr Hudson urged people who wanted to protect Swale's green-spaces to take part.
"It's the only opportunity they will have in next 20 years - don't wait or it will be too late," he said.
Take part in the council's core strategy consultation by going to www.swale.gov.uk/pyo, e-mail firstname.lastname@example.org, or call 01795 417118. Alternatively you can write to Swale Council's spatial planning manager, Swale House, East Street, Sittingbourne, Kent, ME10 3HT.
Article by Stephen Waite, East Kent Gazette