Some other firms, including 3Mand Gallop & Gallop, will be given smaller contracts totalling $400,000 to provide outdoor ad space.

Ms [Sandra Crossfield] said any notion the billboards are being readied for referendum ads is just speculation.

Gallop & Gallop vice-president Tom Rothfels said his firm is guessing that the upcoming ads are for a national referendum that could decide the future course of the country.