The Swedish government is to review Nasdaq's proposed $3.7 billion takeover of OMX amid fears that the deal could force companies listed on the Nordic and Baltic markets to comply with onerous US stock market rules.
The Swedish government has a 6.6% stake in OMX, although it plans to sell the shareholding as part of a national privatisation programme.
However, according to a Financial Times report, Sweden's minister for financial markets Mats Odell is setting up an expert panel to review the proposed merger before the government officially greenlight the deal.
Odell told reporters that the government needs to be sure that US ownership of OMX would not alter "the Swedish model" or undermine the Nordic market's competitiveness.
The investigation will look into issues including supervision, regulation, costs, disclosure and the possible impact on liquidity, says the FT.
OMX has previously said that the takeover would not lead to US regulations being imposed on trading or companies listed on the exchanges it operates in the Nordic and Baltic regions. Furthermore earlier this month, OMX chairman Urban Backstrom and CEO Magnus Booker told reporters that the group had held talks with the US Securities and Exchange Commission (SEC) and that the agency had confirmed that trading and listing on OMX exchanges would not fall under SEC rules.
But despite these assurances the Swedish government is pushing ahead with the investigation and may even vote against the merger deal if it concludes that it will harm OMX's competitiveness.
OMX shares were down SKr5.00, or 2.39%, in mid-day trading on news of the probe.