British telecoms testing services provider Spirent Communications warned of lower annual profit on Wednesday, saying the telecommunications market is "extremely challenged at this time".

The London-listed company said its largest customers were delaying their spending and technology investment, leading it to cut its outlook for the term as negative operating leverage will impact operating profit for the year "very materially".

(Reporting by Yadarisa Shabong in Bengaluru; Editing by Rashmi Aich)