Fossil Free Shropshire delivered the postcards to the fund at Shirehall in Shrewsbury on Tuesday, ahead of a key vote set to take place next week.
The fund's pensions committee – which is made up of councillors from Shropshire Council and Telford & Wrekin Council – will meet to discuss the future of the fund next Monday.
Kris Welch, a spokesperson for Fossil Free Shropshire, said: "These 1,000 postcards, signed by ordinary people from across the county and beyond, send a powerful message to the pensions committee ahead of their vote next week.
"People want to see Shropshire’s flagship fund start taking the climate crisis seriously."
The delivery of postcards comes after a recent report concluded that pulling out of investing in fossil fuels is not in the best interests of 50,000 Shropshire pensioners, although, the report to the pensions committee recommends that the fund commits to a net zero carbon emissions approach from its investments by 2050.
The report follows a motion by Shropshire Council in July 2020 which called on the county's pension fund to stop investing in companies such as BP and Shell by 2023.
Councillor Julian Dean, a Shropshire Green Party Councillor, tweeted that "this plan to keep investing in fossil fuels up to 2050 is murderous to future generations and risky for our pensioners".
COP26 worst bit of green washing came from finance sector. Looks like Shropshire Council pensions committee about to do their own version. This plan to keep investing in fossil fuels up to 2050 is murderous to future generations & risky for our pensioners.https://t.co/qbt8bAwlhJ— Julian Dean (Cllr. Green Party) 💚 (@JulianDean99) January 8, 2022
Ms Welch said: "We are disappointed to see that the announcement of this new report, which hasn’t been made public yet, is being used to predetermine the committee’s vote.
"We would point out that the fund hasn’t actually bothered to ask its 50,000 members their opinion on how their pensions are invested.
"Is it in Shropshire pensioners' best interests to see the planet burn? Is it in pensioners' best interests to invest in a sector that has been less profitable than renewables for the last decade?
"Fossil Free Shropshire believes that the pension fund committee has a stark financial and ethical choice next week.
"Either it continues with business as usual, ignoring all the evidence from scientists and financial experts, or it wakes up and joins the thousands of other pension funds who are rushing for the exits before the carbon bubble bursts."
Shropshire Council have been contacted for comment.