Balance-of-power MP Geoff Shaw has triggered a fresh political crisis for the Napthine government by refusing to guarantee support for the May budget.

After a chaotic week in State Parliament, the Frankston MP demanded fresh discussions with Premier Denis Napthine before this year's budget.

He told The Age there were no guarantees he would support the financial bills that ensure the government can access money to run the state. ''When I went independent in March, the budget was coming up in May so we had that discussion before that budget,'' he said. ''We will be having new discussions this year.''

Mr Shaw made a verbal agreement with the government last year, promising to support it on matters of confidence and supply.