The government has proposed a trademarks amendment bill to accompany its plain pack legislation, stating it would free tobacco companies to use elsewhere the company trademarks which are to be banned from the cigarette packs.

The Coalition's spokesman on the issue, Dr Andrew Southcott, said that the effect of the legislation would enable the government to introduce regulations over-riding trademark law - a rare and worrying extension of executive power.

A government source however said that the intention of the additional legislation was to provide ''an additional level of assurance for trademark owners that the government will be able to regulate quickly to address any areas of ambiguity should trademark protections be challenged as a result of the Tobacco Plain Packaging Bill''.

The legislation is expected to pass with the support of independent MPs, with or without the support of the Coalition.

The addition of the trademark provisions follow criticism, particularly from tobacco companies and some United States politicians, that the government's plan posed an assault on trademark rights.

Yesterday, the Health Minister, Nicola Roxon, said the Opposition Leader, Tony Abbott, had his wrecking ball sights set firmly on plain packaging.

''Tony Abbott needs to prove he's not in the pockets of big tobacco and support both bills to support plain packaging.''

Dr Southcott said that it was ''rubbish'' to suggest that the opposition did not support plain pack legislation.

''We don't think it [the trademark legislation] is necessary for the operation of the plain packaging legislation''.