THE Palmer United Party is suing the two senators who quit it.
PUP leader Clive Palmer announced the party would sue Jacqui Lambie and Glenn Lazarus to recoup the money spent on their election campaigns.
Senator Lambie and Senator Lazarus quit the party leaving the PUP with just one senator, Dio Wang, and Mr Palmer in the lower house.
The party's official Twitter account posted that "Palmer Utd is taking legal action against Senators Glenn Lazarus and Jacqui Lambie for breaking promises to both voters and the party".
Senator Lambie announced on Tuesday she would found her own party, the Jacqui Lambie Network, while Senator Lazarus indicated he intended to remain an independent.
In a statement, PUP national director Peter Burke said Sen Lazarus and Sen Lambie had promised to represent the party for their entire term.
"Relying on those promises, the party spent millions of dollars and thousands of party supporters worked hard to get Mr Lazarus and Ms Lambie elected," Mr Burke said in a statement.
"They have now broken their promises and the party will seek to recover in the courts - under the principle of promissory estoppel - those party funds.
"Australians are tired of politicians saying one thing before an election and then breaking their promises afterwards.
"Party legal advice confirms the strength of the party position under law.
"We have also consulted extensively with our members over these matters, who feel very disillusioned."
Senators Lambie and Lazarus did not respond to requests for comment from APN Newsdesk on Wednesday.
Speaking to the ABC, Mr Palmer said PUP was not suing the senators in relation to whether they could hold a Senate seat or how they should vote.
"We're suing them just to recover the funds that we spent in reliance of their promise before they got elected," he said.