The firms claim to be acting on behalf of shareholders, but no public backing has been declared yet.

According to the Shareholders Foundation, an advocacy group, the investigations will look into whether the price of $50 a share undervalues the company and whether SPSS’s board could have squeezed more from any potential acquirer through an open auction process.

SPSS and IBM have yet to declare in detail how the deal came about. SPSS CEO Jack Noonan has revealed that IBM made the initial approach, though he would not comment on whether SPSS sought alternative bids from other parties. Speaking on a conference call last week, Noonan said: “The process will be defined in the proxy statement”, which is due this week.

Meanwhile the stock market appears satisfied with the price offered by IBM. SPSS’s shares rose 40% to $49 on news of the deal last Tuesday and the price has held level since.

IBM’s purchase of SPSS is subject to approval by SPSS shareholders, applicable regulatory clearances and other customary closing conditions. It is expected to complete before the end of the year.

• In other news today, IBM has opened an analytics solutions centre in China designed to meet what the company sees as “the growing demand for advanced analytics capabilities needed to help clients build smarter business systems and drive improved decision-making”. Analytics solutions centres are already operational in Berlin and Tokyo with others set to launch soon in London, New York City and Washington DC.