RELATIONS between the federal government and Rob Oakeshott have turned poisonous after a senior cabinet minister initiated legal action against the NSW independent MP concerning comments he made about the mining tax.

Mr Oakeshott has been threatened legally by the Minister for Resources and Energy, Martin Ferguson, after comments Mr Oakeshott made to The Sydney Morning Herald last week after it was revealed the mining tax would make next to no revenue in its first three months.

Incredulous ... Independent MP Rob Oakeshott. Credit:Andrew Meares

Mr Oakeshott, whose support is vital to keeping Labor in power and Mr Ferguson in his job, has reacted angrily to the legal letter, which he received on Thursday, describing it as ''stupid''.

''I can confirm I have received defamation proceedings from cabinet minister Ferguson,'' he said on Friday.