Is there a legally mandated filing fee and/or deposit in the last instance?

HOUSE OF ASSEMBLY (ELECTIONS) ACT 14 of 1951, CHAPTER 2:01

Section 68:

“2. at the time of the presentation of thepetition or within three days afterwards, security for the payment of allcosts, charges and expenses that may become payable by the petitioner -

1. to any person summoned as a witness on hisbehalf; or

2. to the member whose election or return iscomplained of, or to any other person named as a respondent in the petition,shall be given on behalf of the petitioner;

3. thesecurity shall be an amount not exceeding twelve hundred dollars and shallbe given by recognizance to be entered into any number of sureities notexceeding four approved by the Registrar of the High Court, or by deposit ofmoney in the High Court, or partly in one way and partly in the other.

Source: http://www.dominica.gov.dm/laws/chapters/chap2-01.pdf

EasternCaribbean Supreme Court (Dominica) Act 10 of 1969, Chapter 4:02

Source: http://www.dominica.gov.dm/laws/chapters/chap4-02.pdf