Public sector pension funds have demanded that Rupert Murdoch's bid to take full control of Sky should offer an "appropriate premium" and be referred to the communications regulator.
The Local Authority Pension Fund Forum (LAPFF) - which represents 71 council funds and controls around 2% of Sky - has joined a chorus of investors angling for an advance on 21st Century Fox's offer of £10.75 per share for the 61% of Sky that it does not already own.
The group said that any tie-up should be based on "an appropriate premium as well as safeguards for future probity given past track records of the businesses controlled by the Murdoch family".
The likes of Standard Life Investments and Jupiter Asset Management have also questioned the offer price, which amounts to £11.2 billion.
The LAPFF said that "robust safeguards" need to be put in place before Murdoch-owned Fox can sew up the deal, adding that "f urther clarity may also be needed so that public shareholders have full confidence that proposals are not being unduly influenced by the well-known relationships between Sky and 21st Century Fox".
When Mr Murdoch last took a tilt at Sky through News Corporation five years ago the company - which owns The Sun and The Times - was forced to abandon the bid after becoming embroiled in the phone-hacking scandal involving News International.
LAPFF chairman Kieran Quinn said: "The role of Ofcom would be helpful in bringing its expert scrutiny on a deal that will have a broader impact on the future of the broadcasting and print media marketplace in the UK."
The decision on whether to ask Ofcom to investigate the takeover will fall to Culture Secretary Karen Bradley, who will have 10 days from when Fox posits a firm bid to decide if the deal should be referred.
The group added that it will "scrutinise the process carefully".