The incoming chairman of convenience store giant 7-Eleven has used a Senate inquiry hearing to apologise for underpaying its workers.

Michael Smith said the company did not condone the underpayment of workers or the breaking of workplace laws.

The inquiry will examine allegations that thousands of workers were underpaid by franchise operators.

Some workers also claimed the company had charged employees up to $70,000 to sponsor their visa.

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“As the new chairman of this company I think it is important for me to say that I am sorry,” Mr Smoth said in his opening statement.

It came amid reports that Prime Minister Malcolm Turnbull had a stake in the global parent company of the controversial franchise chain.

Mr Turnbull had shares in two international investment funds that invested in Japanese conglomerate Seven & I Holdings, Fairfax Media reported.

The wage regulator raided 20 7-Eleven outlets in Melbourne, Sydney and Brisbane seizing rosters, timesheets and CCTV footage from stores it suspected was committing wage fraud.

It found that 60 per cent of franchisees raided were underpaying staff.

Fair Work Ombudsman representatives will also appear at the hearing.