More than 4,000 people have signed a petition to keep the Isle of Wight as one parliamentary constituency.
Electoral reform plans suggest creating constituencies of 75,000 voters but the island currently has 110,000.
Islanders fear the extra 35,000 constituents could be added to a constituency in Hampshire, meaning their MP could be from the mainland.
Opposition group OneWight said support was growing. The Boundary Commission has until 2013 to make recommendations.
Campaign co-ordinator Bob Seely said the plan contradicted previous Boundary Commission reports which recognised the island's unique history and geography and identified significant communication problems in attaching parts to the mainland.
He said: "The Boundary Commission was talking sense and I don't understand what has changed.
"The problem is the Isle of Wight always gets short-changed. I think we, as an island, are being ignored."
Some residents say the island has different needs to the mainland which would be ignored by an MP from the mainland.
The island's MP Andrew Turner is also backing the campaign.
In the proposals, Deputy Prime Minister Nick Clegg said the changes would reduce the number of MPs by 50, to 600, which could save taxpayers up to £12m a year in salaries, pensions and allowances.
He said the only areas not affected would be Orkney and Shetland and the Western Isles, which were considered "uniquely placed".