By Peter Henley
Political correspondent, BBC South
Ms Andreasen became a Euro MP earlier this year
The UK Independence Party (UKIP) can not afford a bitter leadership contest, a senior party member has warned.
South East England MEP Marta Andreasen resigned as the Eurosceptic party's treasurer after a disagreement with party chairman Paul Nuttall.
But she has said she remains loyal to the party, and has called for unity during the leadership contest to replace fellow MEP Nigel Farage.
She told BBC News: "I have a commitment to the people who voted me in."
Mrs Andreasen was fired as Chief Accountant of the EU after blowing the whistle on what she claims was corruption and fraud.
She was elected an MEP in June for UKIP, with a record share of the vote in the South East of England.
But she announced her resignation as party treasurer saying the the party was wasting money and needed "people who are more mature and professional, both in an organisational and political way".
A major party donor, spread betting millionaire Stuart Wheeler has now backed her comments.
He told The Politics Show: "She's a strong minded lady, and she has very strict standards which is a good thing. If she's found deficiencies I'm sure that notice will be taken."
Mr Wheeler said he had assurances from former leader Nigel Farage that his resignation was not connected to the disagreement.
And Mr Farage has also assured members that Andreasen's resignation was only "an internal tiff".
"I wouldn't have handed over the leadership now if I thought we had a party that was split, if I thought we had a party that had problems.
"She's made an immeasurable improvement to the party - but her parting shot is that there's still a long way to go - I don't disagree with that."