Aurelius Capital, a minority Clearwire shareholder, is suing the directors of Clearwire and Sprint Nextel, unhappy at the merger agreement struck between the companies last December.

According to a Reuters report, Aurelius – a hedge fund which owns 17 million shares in the cash-strapped US wholesaler of capacity – claimed the directors of both firms “violated their fiduciary duties to Clearwire’s minority shareholders”.

Specifically, Aurelius says Clearwire chairman John Stanton should not have led negotiations with Sprint since he was originally nominated to the Clearwire board by the US mobile operator. Sprint already owns a 51 per cent stake in Clearwire.

Crest Financial, another large Clearwire shareholder, has also spoken out against the Sprint deal.

Fuelling shareholder anxiety is the fact that the Sprint offer, which valued Clearwire at $2.97 per share, is well short of a counter bid made in January by US satellite TV company Dish Network, which is worth $3.30 per share.

At the close of trading Friday, the Clearwire share price stood at $3.44.

In another twist, Verizon Wireless made an unsolicited offer on 8 April to buy spectrum leases held by the wholesale operator. According to Clearwire, the offer is worth a gross price of between $1bn and $1.5bn to cover around 5 billion MHz-POPs in large markets.

Walter Piecyk, a BTIG anyalyst, says the bid values Clearwire’s spectrum at between $0.20 and $0.30 per MHz for each person covered. By contrast, says Piecyk, the Sprint offer values Clearwire spectrum assets at $0.21 per MHz per person.

At the announcement of its Q1 results on 25 April, Clearwire said it was still evaluating the Verizon Wireless offer. The company also maintained it had enough cash to fund its operations until Q1 2014, but that would mean cutting back on network upgrades.

A Clearwire shareholder vote on the Sprint agreement is scheduled for 21 May.