Senate powerbroker Rex Patrick said the Tax Office and financial regulators should disclose how many Australian companies have links to the Cayman Islands, after the government said it did not keep data on firms connected to the notorious overseas tax haven.

The Centre Alliance's key negotiator slammed Treasurer Josh Frydenberg over answers to questions on notice to the Senate about the number of Australian companies that are subsidiaries of firms based in the Carribean territory, a known destination for tax avoidance.