United Future Peter Dunne is expected to spend the week settling into his much smaller office at Parliament and preparing his party's case for a special meeting of the Electoral Commission.
The outcome of the Electoral Commission meeting could affect whether Mr Dunne loses $100,000 of his leaders' budget at Parliament.
After resigning as a minister on June 7, Mr Dunne took leave from Parliament last week.
This week he will seek to persuade the commission that it should change its policy to accept electronic evidence of his party's 500 members and paid fees - as it does with registered parties - rather than require United Future to present original signatures as is required with new parties. That could take months to collect and would be an even greater setback to rebuilding the party's presence in Parliament.