....over the payment of a $56.25m (£35.5m) rent cheque due last Saturday. Inmarsat, which is headquartered in London, yesterday (February 20, 2012) issued a notice of default to the U.S. wireless company, citing an unpaid multi-million payment due upon the completion of the “phase one transition”.

LightSquared proclaimed its innocence, claiming that Inmarsat neglected to fulfill its obligations required for the completion of phase one.

LightSquared, which provides wholesale-only 4G networks, has recently come under fire in the US on claims that its services interfere with GPS provisions operated from a neighbouring spectrum.

But an Inmarsat spokesperson told City A.M., “We are confident that we have fulfilled everything we are required to do under phase one of the agreement.” LightSquared now has 60 days to come forward with the due payment, otherwise Inmarsat will reclaim the 10MHz of spectrum it currently loans to LightSquared and gain a further two MHz of range owned by the American company.