The Prime Minister and Opposition Leader are expected to support Labor candidate Darren Cheeseman and Liberal candidate Sarah Henderson in their fight for the ultra-marginal Corangamite.

However, the major party leaders are less likely to venture further than Colac, which is one of the largest cities in the tightly-fought seat held by Labor on a slim margin of 0.9 per cent.

Independent Ralph Leutton said Ms Gillard and Mr Abbott had ignored Wannon because it was a safe seat.

"I issue this as a challenge - if you are really interested in having your party representing Wannon, come here during the campaign," he said.

"Wannon is just as important to its residents as the tightest, most marginal seat is to its local residents. But because we are not marginal we continue to be taken for granted."

Former prime minister Bob Hawke visited Colac last week and Ms Gillard is expected to campaign with Mr Cheeseman in the south-west city before election day on August 21.

Independent candidate Allan Marsh said the nation's party leaders should bypass Colac and head straight to Warrnambool.

"Colac is really a gear change on the drive to Melbourne, why would Gillard or Abbott want to stop there and not come to Warrnambool," he said.

"I challenge the two of them to come to Warrnambool and enjoy a Kermond's hamburger."