The concerted campaign was uncovered after the Mercury discovered that of 280 submissions to the electoral authority objecting to the redistribution of seats right around the state, a quarter are uniform letters objecting to the plans for Gilmore.

The proposed change would see Gilmore gain 20,000 traditionally Labor voters from areas including Shellharbour, Barrack Heights and Albion Park, while losing 14,000 more conservative electors in Eurobodalla.

Gilmore, held by Liberal Joanna Gash with a margin of 4.1 per cent, would become a knife-edge nominal Labor seat.

"They're pretty worried - the new boundaries would leave us with a tough fight for Gilmore," one South Coast Liberal said.

The form letters have been sent in a range of fonts.

All have been signed and addressed by different people - several who have direct links with Liberal Illawarra and South Coast politicians.

The practice of sending form letters is allowed under electoral commission rules.

The letter states that any seat "that includes the Shoalhaven local government area and urban southern suburbs of Wollongong will only take away the regional voice and representation of the Shoalhaven area".

"Bringing the Shoalhaven and Wingecarribee local government areas together in the division of Gilmore would mean the interests, common to our rural communities, are directly represented in the Parliament," the letter reads.

This view is supported in the official Liberal Party submission and those of other South Coast and Southern Highlands bodies.

Labor-held seats in the Illawarra, Throsby and Cunningham would see a reduced margin under the proposed changes but are still safe.

However, both parties have issues with Throsby taking in the Southern Highlands.

Nominations for Liberal pre-selection in Gilmore closed on Friday. Mrs Gash is the only nominee and is now almost certain to be the candidate at the election.

She denied knowledge of the letters and campaign.

Several Liberal sources and some people who signed the letters confirmed that branches on the South Coast distributed them, asking people to sign and send them onto the electoral commission.

"Whatever happens, will happen," Mrs Gash said of the proposed changes.

"As far as I'm concerned, my head is already in the north."